Assessment of the Geotouristic Values of Devil’s Town, Serbia

Serbia is a country rich in geoheritage with eighty geomorphological sites now under protection. Although a canyon, the site of Devil’s Town is a unique geomorphological site in Serbia and deserves special attention. The geotouristic values of Devil’s Town were assessed based on the analysis of its present state and comparison with three similar and nearby geosites on the Balkan Pennisula (the Sand Pyramids in Bosnia and Herzegovina and the Stob and Melnik Earth pyramids in Bulgaria). The assessment was performed using a ‘modified geosite assessment model’ (M-GAM), which includes estimation of the main indicators and sub-indicators. Devil’s Town has an average level of major and additional values. Indicators show that this geosite has great tourist, scientific and aesthetic value, as well as enough space for improving the ecological and functional values, as a basis for the development of tourism. Devil’s Town displays a higher touristic value than the Sand pyramids and slightly lower than the Stob pyramids. However, in comparison with the Melnik Earth pyramids in Bulgaria, its touristic value is significantly lower. This study could serve as a guide for managing development strategies concerning decision-making and engagement in tourism of the analysed geosite, addressing the needs of modern tourists. However, the geotourism potential and geoturist values of this geosite remain partially hidden. The promotion of geological and geomorphological heritage is growing in importance when it comes to cultural tourism and landscape valorisation as thematic excursions and itineraries (REYNARD, 2009). The first official definition of geotourism was given by Thomas Hose, (1995,1996), and later reformulated (HOSE, 2000). Geotourism, as a geoscience­based tourist activi ty, is a process of recognizing and giving a wider meaning to geoheritage objects in order to preserve them more effectively (HOSE, 2005a). A straightforward definition was given by JOYCE (2006), who defines geotourism as a situation where “people go to certain places to observe one or more aspects of geology and geomorphology and learn about them.” The definition of geo­ tourism given by GRAY (2008), takes a view on the need for geo­ conservation; “Tourism is based on geological and geomorpholo­ gical resources of an area that attempts to minimize the (negative) impact of this tourism through geoconservation and sustainable management”. Under geoconservation, BUREK & PROSSER (2008) include active site management in order to preserve the original state and prevent any changes. Geoconservation measures in combination with the promotion of tourism are the most impor­ tant elements of geotourism (HOSE, 2005b). SADRY (2009) states that geotourism is in fact knowledge­based tourism, interdisci­ plinary integration of the tourism industry with conservation and interpretation of the attributes, abiotic in nature, in order to bring the geosite closer to the general public. NEWSOME & DOWLING (2010) have come to the conclusion that geotourism promotes tourism at geosites as well as the conservation of geodiversity and understanding of the geosciences by means of respect and understanding (learning). The latest definition of modern geo­ Article history: Manuscript received May 19, 2020 Revised manuscript accepted March 22, 2021 Available online June 30, 2021


INTRODUCTION
Although Serbia is a small European country, it has a rich geo heritage. There are numerous geological and geomorphological sites, which are excellent representatives of geodiversity. The cur rent inventory of eighty protected geoheritage sites includes about 650 geological, hydrogeological, palaeontological, geomorpho logical, spelaeological and neotectonic phenomena (DJUROVIĆ & MIJOVIĆ, 2006, VASILJEVIĆ, 2015. There are numerous geosites with unique diversity, which can provide authentic and unforgettable experiences to tourists. Such an environment pos sesses an outstanding opportunity regarding geotourism deve lopment. Devil's Town is an excellent representative of rich natu ral heritage and it can potentially represent high geotouristic values being as one of the protected geomorphological geoherita ge sites (STANKOVIĆ, 2004) and the most important geomor phological monument of nature in Serbia formed by erosion (RISTIĆ et al., 2018). Concerning major geostructures designated to geodiversity, Devil's Town considers "geomorphological oc currences, erosion and depositional proccesses and landscapes'' (DJUROVIĆ & MIJOVIĆ, 2006). The site is classified into the First category of protected sites, i.e. the category of natural mon uments of outstanding importance, and has been declared a geo logical monument of nature. Regarding topography, the area is highly diverse. The occurrence of 202 stony topped Earth pillars (French term ''demoiselle''; North American term ''hoodoo''; in cluding universal terms: ''pedestal rocks'', ''rock pinnacles''; ''Earth pinnacles'', Earth pillars'', ''rock pillars''; Earth pyra mids) is noteworthy. These are rare natural phenomena resem bling very attractive denudation relief forms (gullies are the most dominant forms, including groundwater seepages and scars).
However, the geotourism potential and geoturist values of this geosite remain partially hidden.
The promotion of geological and geomorphological heritage is growing in importance when it comes to cultural tourism and landscape valorisation as thematic excursions and itineraries (REYNARD, 2009). The first official definition of geotourism was given by Thomas Hose, (1995,1996, and later reformulated (HOSE, 2000). Geotourism, as a geosciencebased tourist activi ty, is a process of recognizing and giving a wider meaning to geoheritage objects in order to preserve them more effectively (HOSE, 2005a). A straightforward definition was given by JOYCE (2006), who defines geotourism as a situation where "people go to certain places to observe one or more aspects of geology and geomorphology and learn about them." The definition of geo tourism given by GRAY (2008), takes a view on the need for geo conservation; "Tourism is based on geological and geomorpholo gical resources of an area that attempts to minimize the (negative) impact of this tourism through geoconservation and sustainable management". Under geoconservation, BUREK & PROSSER (2008) include active site management in order to preserve the original state and prevent any changes. Geoconservation measures in combination with the promotion of tourism are the most impor tant elements of geotourism (HOSE, 2005b). SADRY (2009) states that geotourism is in fact knowledgebased tourism, interdisci plinary integration of the tourism industry with conservation and interpretation of the attributes, abiotic in nature, in order to bring the geosite closer to the general public. NEWSOME & DOWLING (2010) have come to the conclusion that geotourism promotes tourism at geosites as well as the conservation of geodiversity and understanding of the geosciences by means of respect and understanding (learning). The latest definition of modern geo tourism was developed by HOSE & VASILJEVIĆ (2012): "Pro viding interpretative content and services at geosites, geomor phological sites and the surrounding topography, together with related insitu and exsitu artifacts, in order to conserve them, improve their appreciation, education and scientific work both [by, and] for, the present and the future generations." The basic principles of the fundamental importance for geo tourism are: geological basis, sustainability, geointerpretation, benefit to the local community and tourist satisfaction (DOWL ING, 2011). The economic perspective should also be taken into account. Geosites as a basis of geotourism development contribu te to both the original and the additional tourist offer (PRALONG, 2006). In the context of geotourism, geoheritage provides the original offer. The additional offer consists of the infrastructure, goods and services offered to tourists in order to complete, improve and facilitate their visit. These can be informative and interpretative boards, the construction of paths and lifts to hard toreach places, or the organization and training of the guides (PRALONG & REYNARD, 2005;REYNARD, 2008). Tourist exploitation of geography can have a negative impact on Earth systems (NEWSOME & DOWLING, 2006;HOSE, 2008;HOSE et al., 2011;HOSE & VASILJEVIĆ, 2012) which can lead to deg radation and an increase in the vulnerability of the geodiversity. Thus, it is necessary to create such an offer that will bring geo logical and geomorphological knowledge and scientific achieve ments to all visitors, as well as enabling the undisturbed and im proved development of tourist activities.
Serbia has the potential for an increase in geotourism but is obviously lagging behind countries with developed tourism. Hence, the main goal of this study is to assess the geotouristic values of Devil's Town and its comparison with the three simi larly featured and nearby geosites in the Balkans (Sand Pyramids in Bosnia and Herzegovina and Stob and Melnik Earth pyramids in Bulgaria) by applying the MGAM model. The results obtained should point to the potential advantages and disadvantages in these analyzed localities as well as to the main future tasks of management during the planning and development of a tourist offer aiming to adjust these to attractive tourist destinations.

Study area
Devil's Town spatially belongs to the municipality of Kuršumlija, and the village of Djake on Radan Mountain (central part of Southern Serbia). It covers an area of 8.31 ha, at an altitude of 660 -796 m a.s.l. The Devil's Town is located 290 km from Belgrade, 29 km from Kuršumlija, and 9 km from the state road IB category no. 35 NišPriština. Beside this state road, there is also the Niš Prokuplje Kosovo Polje railway. The closest airports are Slatina in Priština (57 km) and the airport in Niš (92 km). Prolom Banja, which is one of the most visited spas of great touristic value in Serbia (TOMIĆ & KOŠIĆ, 2020), is located nearby, 28 km from Devil's Town. These two touristattractive destinations are con nected by a wellbuilt hiking trail. Parking for vehicles is 850 m away from Devil's Town, and the hiking trail leads to the top of the erosive fountain with a viewpoint that allows sightseeing and photography of the stone formations. At the beginning of the hik ing trail, several ethnostyle mountain lodges were built, one housing a restaurant with food prepared in the traditional Serbian style and an art galery where the photocontest "Devil's Town" is traditionally held in May each year (Fig. 1).
Regarding geology, Devil's Town is located within the Lece volcanic complex, which is one of the largest Tertiary volcanic provinces in Serbia. It is, (observing the geotectonic setting), situ ated along the boundary between the SerboMacedonian mass (SMM) to the east and the Eastern Vardar zone to the west (Fig.  2). These two units are delineated by the Propolac-Medvedja and Tupala dislocation (STAJEVIĆ, 2004). The former unit has been interpreted as part of the deformed margin of the Eurasia conti nental plate, while the latter is considered a remnant of the vast Tethys Ocean (e.g. SCHMID et al., 2008).
According to the generally accepted explanation, the volca nic complex of Lece was formed in response to the Dinaride col lapse. Magmatism took place along dextral strikeslip faults that resulted in transpressive crustal shortening and collision of the SMM as a part of the European plate within a short time frame, from about 33 to 31 Ma (DRAGIĆ et al., 2014;TOSDAL, 2012).
The unique geomorphological phenomenon in Serbia con tains about 202 stone formations formed on steep slopes of two deep, parallel cut gullies. The formations are of different shapes and sizes. The oldest ones are the highest, up to 17 m high, and they are placed at about 670 m a.s.l., while smaller forms are up to 2 m high and are placed at about 680 to 700 m a.s.l. Today, it is very easy to find videos of Devil's Town on the internet.
These specific natural formations are the result of an erosive process that lasted for at least two hundred thousand years, dur ing which those formations evolved and passed through different stages of development. The Devil's Town rocks are andesitic vol canic and volcaniclastic rocks and have been protected since 1959. In 1995, the Decree of the Government of the Republic of Serbia proclaimed a site of National importance" and placed into the highest category of protection. A total area of 67 hectares is protected, although there is a requirement to increase the pro tected area to 1014 ha.

Geological background
The geology of the broader area is presented on the Basic Geological Map 1:100.000, sheets Kuršumlija and Podujevo (MALEŠEVIĆ et al., 1974;VUKANOVIĆ et al., 1975). The old est rocks are Cambrian gneisses and subordinate Devonian meta morphosed limestone. Broad areas cover Cretaceous products, conglomerate and flysch sediments associated with members of the Jurassic ophiolite mélange (previously known as the "diabase chert formation" . The most dominant lithological units are products of Oligocene vol canism with a formation age of 32-28 Ma (KARAMATA et al., 1992;KOSTIĆ et al., 2017). These volcanic products are andesites and volcaniclastic rocks including lava flows, pyroclastic brec cias, crystalline and lapilli tuffs (DIMITRIJEVIĆ & DRAKULIĆ, 1958;DRAGIĆ et al., 2014). Andesite displays a porphyritic tex ture, and contains plagioclase (Fig.3a), amphibolehornblende ( Fig.3b), biotite (less frequently) and monoclinic and orthorhom bic pyroxenes as phenocrysts. Accessory constituents are apatite and opaque minerals. Their uniform chemistry suggests uniform volcanism within the entire complex (JOVANOVIĆ et al., 1972). Negligible variations in chemistry could be a consequence of minimal changes of steam pressure inside a volcanic vent or in ternal diffusion during peaceful phases as well as hydrothermal action and subsequent alteration (JOVANOVIĆ et al., 1972). Py roclastic rocks, including some wellbonded ignimbritic types, comprise horizons from a few 100 m thick. Hydrothermally al tered rocks are most abundant in the area of interest occurring as reef zones due to their higher resistance (Fig. 3c, d). The most intensive hydrothermal process is silicification revealing the re markable, several kilometers long zone of silicification known as the "quartzosebrecciated zones" (PEŠUT, 1976). At higher ele vation, intense phyllic alteration occurs, which encompasses the mineralized rocks (DRAGIĆ et al., 2014). Hydrothermal altera tion developed along favourable volcanictectonic and tectonic rupture systems (STAJEVIĆ, 2004). Fissures about 1km in length prevail, although some exceed a few km. In the same fracture zones precious minerals occur together with galena, sphalerite, pyrite and gold (e.g. the Rasovača, Vrtače, Kameno rebro and Bučumet deposit). Precious silicate minerals include amethyst, amethystagate, agate, fibrous chalcedony, granular quartz and relic opal, which display very heterogeneous colour varieties (MILADINOVIĆ et al., 2010). Although gemstone deposits be came the subject of interest after World War II, on the basis of certain archaeological finds it is known that the amethyst and ag ate had been exploited by the Ancient Romans. Numerous poorly explored occurrences, mostly placer deposits (eluvial, deluvial, proluvial and alluvial), distributed outwith the volcanic complex, i.e. on its eastern rim also exist. Volcanic products affected by si liceous and/or siliceousmineralized hydrothermal fluids were later exposed to further weathering and erosion along the already existing fissures.
Volcanoes in this area undoubtely exceeded 1000 m in height (Gajtan caldera in spite erosion and shortenning reaches approxi mately 700 m a.s.l.). Devil's Town is the largest and most complex caldera with a diameter of about 25 km. The best preserved parts are at Sokolovica (in the north) and at Markov Vis (in the south).

Relief shaping
Volcanism initially sculpted this area in the Palaeogene, i.e. Up per Oligocene (DIMITRIJEVIĆ & DRAKULIĆ, 1958). Accord ing to JOVANOVIĆ et al. (1972) andVALJAREVIĆ et al. (2015) volcanic activity evolved throughout three phases: 1. Development of stratovolcanoes (emitting both tephra and viscous lava, building steep conical mounds), 2. Formation of calderas, and 3. Subsequent processes inside the calderas and consolida tion of the entire complex. 1. Stratovolcanoes (complex, composite or gray volcanoes) are large, longlived volcanoes, particularly those of andesitic com position that emit a combination of lava flows and tephra, building steepsided volcanic cones. A growing lava dome might exceed 1000 m in height, as lava flows resist or slow down erosion and loss of tephra. The beautiful steepsided cones of stratovolcanoes are among Earth's most picturesque sights (e.g. Mount Fuji in Japan, Mount Rainier and Mount St. Helen in Washington, former volcanoes in East Serbia etc.). The height of volcanoes in this area undoubtely exceeded 1000 m (as the Gajtan caldera is now, although eroded and shortened, nearly 700 m), with a basal diameter greater than 30 km. Stra tovolcanoes are often transformed over time as calderasroughly circular basins, the diameter of which can vary be tween 1 25 km, some of which are still preserved as relics. In general, a caldera develops by collapse after the partial or com plete emptying of a magma chamber. The unsupported roof of the empty chambers sinks slowly under its own weight. 2. Caldera dimensions exceeded the dimensions of the former vol canic cones. Pyroclastic rocks as well as lava flows in the relics of former stratovolcanoes generally dip towards the volcano periphery, if not affected by subsequent tectonic events. Devil's Town is, as mentioned above, within the volcanic complex of Lece, a subvolcanic PbZn deposit, which consists of three large calderas: Gajtan, Devil's Town and Tulari. However, at present, a significantly larger number of smaller calderas and volcanic vents are being observed (SERAFIMOVSKI, 1990;DRAGIĆ et al., 2014). As a result of pronounced erosion ac companied by the effects of endogenic (volcanic) movements within the calderas. Their height can not be precisely deter mined. The Gajtan caldera is the oldest one with only the east ern part preserved at Petrova gora. The southern part was eroded, whereas the western and northern parts were destroyed during development of the Devil's Town caldera. The Tulari caldera is the smallest and the best preserved suggesting that it is the youngest one. It has a complex fabric with a recognizable northward migration of the centre of effusion. The youngest ef fusion centre is still preserved in the form of the neck (Braina) from where a radial dyke stretches towards the north. Devil's Town caldera with a diameter of about 25 km is the largest and most complex, consisting of three smaller calderas: Devil's Town, Ivan Kula and Kravari. Tectonic activity and faulting during the northward migration of its eastern part additionally destroyed and reworked it. The best preserved parts are at Sokolovica (in the north) and at Markov Vis (in the south). Their marginal parts are composed of pyroclastic rocks, while the in ternal parts (morphologically higher and closer to the inner cal dera) are of alternating pyroclastic rocks and lava flows. The outer zone is marked with well sorted material, according to grain size. Tuffaceous sandstone and volcanic gravel overlie crystalline schists and Cretaceous flysch in the footwall. Vol canic breccias and agglomerates build the highest levels. The interior is composed of coarser volcanic products: agglomera tes, breccias, volcanic bombs (2030 cm in diameter), and boul ders reaching a few metres in size. Volcaniclastic rocks are rep resented by a mixture of coarsegrained blocks (from a few decimetres to a few metres in size) and finegrained material explosively ejected from volcanoes. The pillars roofs are of an desite or dacite lava, which like umbrellas either protects them or slows down further erosion and destruction. 3. The presence of sinterized tuffs and younger lava flows in the Gajtan caldera, including repeated volcanic activity in the Tu lare caldera, reflects the continuation of volcanic activity within the previously formed calderas. During the final vol canic phases, after consolidation of the magmatic masses, ba sal uplift in the form of domas took place enabling the devel opment of radially distributed fissures through which hydrothermal solutions percolated. Hydrothermal solutions, meso to epithermal, affected the host rocks which were sub jected to physical and chemical weathering and erosion. These processes finally shaped this area. The stone formations were dissected into twenty metre thick layers of weathered delluvial material (i.e. debris flow) and their growth was enabled by the existence of "caps or roofs" of more resistent material (lava flows) (Fig. 4). Similar forms have been noted in the high mountain ranges of the Andes and Alps (e.g. both sides of the Brenner pass, in Austria, Italy and France etc.), where they were formed through leaching of glacial (moraine) material. Spectacular forms in the Garden of the Gods (Illinois, USA) were formed within sedi ments (red and white sandstone, limestone and conglomerates of Carboniferous age, about 320 Ma old) that were deposited hori zontally, but later have been tilted vertically and faulted by im mense mountain building forces (SKINNER & PORTER, 2000). In the Sahara desert, the Memuniat formation was created within the Ordovician sandstone. However, in Devil's Town, stone for mations are more abundant, larger in dimensions and more resist ant, providing a representative example of the diverse erosive ac tion of water supported by lithological differences and rare hydrothermal occurrences (Fig. 5).
The wider area of Devil's Town is rich in ore (iron, alu minum, gold and silver), and demonstrates mines dating back to the 13th century and the arrival of German Saxon miners (Fig.  6). In fact, the Saxon miners restored mines and the oreforming sites known from the Ancient and the Prehistoric ages. The nearby Neolithic site (5500 to 4700 B.C.) in the village of Pločnik, near Prokuplje, preserved a significant number of prehistoric metalmade weapons and copper tools. These artifacts suggest that this site was a centre of metallurgy in Europe dating back to 55004800 B.C., i.e. that the Copper Age started in Europe ear lier than previously understood. It is also thought that the ore was obtained from an azurite and malachite deposit from the site in the vicinity of Toplica and Kosanica, as neither immediate loca tions of ore excavation nor slag residues resulting from smelting were discovered (ĆUZOVIĆ et al., 2004). Additionally, the re mains of the medieval fortification constructed on the basement of the former Roman settlement of Hammeum (second half of 1st century), were discovered at Hisar hill (Prokuplje). This site is also under state protection and considered to be a monument of great cultural importance.
The entrances to the mine shafts are very narrow, which is characteristic of the castle mines. One of the three preserved mine shafts has been explored. Its entrance is expanded and its length is about 800 m (http://www.djavoljavaros.com/).
There are two rare hydrological phenomena in Devil's Town, related to the last phases of vulcanism. Extremely cold and acidic water (pH 1.5), highly mineralized (15 g / l, most of Si, Al, Fe and S) with a hardness of about 21,050d springs in the upper part of the Devil's Gully. This spring is known as the "Devil's Water".   One litre of water contains over 1.5 g of metal (Al, Fe, K, Cu, Ni) and 2.63 g of sulfur. Due to its very low pH, this water is also a good solvent, suggesting that some amounts of Al, Fe and K were probably extracted from the surrounding rocks. Water in the spring called "Crveno Vrelo (the Red Spring)" (to the right side of the Yellow Stream, about 400 m from the previously mentioned spring) is less acidic (ph 4.0) and ironrich (198.8 mg / l). The oxidized iron along with substances which came from the sur rounding rocks led to changes in the water properties in the stream revealing its name "Žuti Potok (Yellow Stream)". The wa ters of both springs have no healing properties, but they are a natural poison to the living world (PROTIĆ, 1995; http://www. izjznis.org.rs/; SREĆKOVIĆBATOĆANIN, D. et al., 2010) (Fig. 7).

Examples of similar localities in the Balkans
Geolocalities in structure and origin similar to Devil's Town (GS 1 ) in the Balkan area include: the Sand Pyramids (GS 2 ) in Bosnia and Herzegovina and Stob (GS 3 ) and the Melnik Earth pyramids (GS 4 ) in Bulgaria (Fig. 8).
Small peaks called "pyramids" appear in the southeastern most part of the macro region Bosansko Sredogorje near the vil lage of Daničići (location Šljivovice, 9 km from Foča in Bosnia and Herzegovina). Similar landmarks are noted in the vicinity, too. These forms consist of alternating Pliocene clastites -con glomerate, gravel and sand derived in eluvial relief from the for mer Miocene basin under the triggered action of proluvial and gravitational processes during the Quaternary. The sand pyra mids represent a classic example of selective denudation due to the existence of more resistant layers of Pliocene conglomerates in the hanging wall (LEPIRICA, 2013). Continual erosion facili tates their persistent growth.
Sculptured sand columns rise from a broad base and narrow towards the top revealing amazing geomorphological phenomena within the area. These sand pyramids were protected by a decla ration of the Commission to Preserve the National Monuments of Bosnia and Herzegovina in 1959. At present the Institution is revising the inventory of localities that have been protected up to 1992. Due to its outstanding importance, specific protection mea sures are suggested for this locality. It needs to be evaluated in the sense of tourism, bearing in mind that it is commonly com pared to the Devil's Town in Serbia (LEPIRICA, 2010).
The Stob pyramids, known as hoodoos, are located between the western foothills of Rila Mountain and the eastern localities of Kulski rid and Tsarkvishteto near the village of Stob, about 5 km from the city of Kocherinovo (Kyustendil Province) in Bul garia. This site is very popular, in many ways like the Melnik pyramids on the slopes of Pirin Mountain, (Bulgaria) and Devil's Town in Serbia. The site is insufficiently explored and informa tion concerning it remains far behind similar localities elewhere in the world (e.g. the Wheeler geological area in the USA and Cappadocia in Turkey). These erosive landmarks, up to 12 m in height with a stony top, up to 120 cm in diameter, occupy an area of about 7.4 ha at 600 to 750 m a.s.l. The pyramids are composed of weakly bonded NeogeneQuaternary sandstones and conglom erates deposited within the last 1-2 Ma on the slope in a lacus trine environment.

21.
More than 50 km 50 to 20 km 20 to 5 km 5 to 1 km Less than 1 km

22.
None Low quality Medium quality High quality Utmost quality

24.
None Low Medium High Utmost

25.
None Low Medium High Utmost

27.
More than 25 km 10-25 km 10-5 km 1-5 km Less than 1 km The Stob Earth Pyramids were declared a natural landmark in 1964. Their formation, evolution and destruction are taking place in repeated stages driven by groundwater, temperature in version and wind. At the immediate site, two evolutionary stages could be recognized. The site is easily accessible to visitors via designated pathways and viewpoints, which offer a panoramic view over the whole geosite and nearby settlements (Stob, Poromi novo, Barakovo, Kocherinovo, Rila). In the immediate vicinity of Stob village, there are also ancient ruins that should be evalu ated in terms of tourism (https://www.andreyandreev.com/en/ stobpyramidsbulgaria/).
The Melnik pyramids are considered to be the most interest ing natural wonder in Bulgaria, as well as on the Balkan Penin sula. These pyramids are similar to those at Stob, but are much greater in size and spatial distribution. The Melnik pyramids are located on the southwestern slope of Pirin Mountain at about 180 km south of Sofia, in the Blagoevgrad Province and the munici pality of Sandanski. The exact sites are Melnik, Gorna Sushitsa, Karlanovo, Rozhen and Sugarevo. This geosite has been pro tected since 1960 (enlarged and redeclared in 1978) over an area of 1165.6 ha. Rock formations resembling pyramids are located from 350 850 m a.s.l. Their variable colours and heights offer an amazing, very attractive image. The increasing number of visitors from all over the world required a number of buildings and recreation centres to be built in Melnik.
The Melnik region consists of grayishwhite Pliocene sand, mixed with clay layers. It was deposited at the bottom of a shal low lake 3-5 Ma ago. Folding caused by the collision of continen tal plates led to the formation of mountain ranges, such as Pirin, Ograzden and Belasica. The lake water flowed to the south and discharged into the Aegean Sea. In the newly formed valley, ter rigenous material was brought by mountain rivers and streams leading to the formation of about 500600 m of alluvial deposits of weakly cemented and reddish sedimentary rocks. Over the next thousands of years, sediments accumulated up to 120 m thick, nourished from the Pirin range by mountain rivers and streams. In the variously shaped valleys the pyramid formation was addi tionally supported by wind action and temperature inversion.
The Melnik pyramids are of noteworthy shapes and of vari ous sizes that are subjected to changes due to the decomposition and decay of plants, such as deciduous trees, bushes and grasses that thrive there. The most visited pyramids are those located near the Rozhen Monastery. They are easily accessible by constructed pathways from the city of Melnik to the Rozhen monastery. The other attractive group of pyramids is in the village of Karlanovo. Although there are only four pyramids, they look impressive ex ceeding 100 m in height, having slopes barren of vegetation and with flattened peaks. The stony caps have the same protective role against erosion, as in the previously mentioned localities. The small city of Melnik, additionally contributes to the attractive ness for tourists. Renowned for its authentic architecture from the renaissance era it is declared an architectural reserve. Addi tional anthropogenic tourist values include: the Kordopulov House -a large house from the Bulgarian national revival period, Wine Museum, Rozhen monastery -the biggest Orthodox Church in the Pirin Mountain area.

Methodology
Andesite samples were optically analyzed using a petrographic polarized microscope for transmitted light (Leica DMLSP), which is connected to a Leica DFC290 HD camera over the pro gram LAS V4.
The GAM is defined as a simple equation, a sum of 12 sub indicators of the Main Values, and 15 subindicators of the Ad ditional Values which are graded from 0 to 1:

GAM = MV + AV
(1) where MV and AV represent the symbols for the Main and Addi tional Values. We derive these two equations, because Main and Additional Values consist of three or two groups of subindica tors,
A matrix of Main (X axes) and Additional Values (Y axes) is created according to the results. The matrix is divided into nine fields represented by Z(i,j), (i,j=1,2,3). Depending on the final score, each geosite will fit into a certain field. For example, if a geosite's Main Values are 7 and additional are 4, the geosite will fit into the Z 21 field (Figure 9).
High precision and applicability at several geolocalities JONIĆ, 2018;ANTIĆ et al., 2019;VUKOVIĆ & ANTIĆ, 2019; were the main reasons to introduce the importance factor (Im) that has been presented by BOŽIĆ & TOMIĆ (2015). The importance factor (Im) is the mean value for each subindicator given by tourists. A few more papers concerning the use of MGAM (PĂL & ALBERT, 2018; ANTIĆ  BRATIĆ et al., 2020;TOMIĆ et al., 2021) have been published in the most recent few months. The importance factor (Im) is defined, as: Where Iv k is the assessment/score of one visitor for each subin dicator and K is the total number of visitors. Note that the Im pa rameter can have any value in the range from 0.00 to 1.00. Finally, the modified GAM equation is defined in the following form: As it can be seen from the M-GAM equation, the value of the im portance factor (Im), which is rated by visitors (for each subin dicator separately) is multiplied with the value given by experts (also separately for each subindicator). This is done for each sub indicator in the model. Therefore, the values of M-GAM subin dicators are always less or equal to the GAM values (Table 2).

RESULTS AND DISCUSSION
The unique geomorphological phenomenon in Serbia, the Devil's Town, (GS 1 ), was being considered with respect to three similar localities on the Balkan Peninsula, the Sand pyramids (GS 2 ) in Bosnia and Herzegovina, and the Stob (GS 3 ) and Melnik pyra mids (GS 4 ) in Bulgaria. Geosites were evaluated using the above mentioned methodology (MGAM). Values for the Main indica tors and subindicators are given in Table 2, whereas the final re sults of these values are presented in Table 3 and Figure 9.
According to the results obtained, Devil's Town (GS 1 ) dis plays the highest scientific/educative value of the analyzed ge osites, being particularly emphasized by its representativeness. This could be explained by the high didactic and educational characteristics of the locality itself. The Melnik pyramids (GS 4 ) are also known by their representativeness due to features of the geosite. However, the Sand pyramids (GS 2 ) and Stob pyramids (GS 3 ) geosites are of significantly lower scientific value. The knowledge on their geoscientific issues has the lowest value within the analyzed subindicators of scientific value of all of the analyzed geosites. The lowest number of publications relates to the Sand pyramids (GS 2 ), while articles for the rest of geosites were commonly published in local publications, less commonly in regional and national journals. The Stob (GS 3 ) and Melnik pyramids (GS 4 ) also record low values for rarities, as both ge osites are in Bulgaria in the circled area of 100 km.
Concerning scenic/aesthetic values, the Melnik pyramids (GS 4 ) exhibit the highest values due to the amazing landscape and beautiful natural scenery in the vicinity: a number of desig nated viewpoints, contrasting colours and shapes, as well as the overall appearance of the geosite. The Stob pyramids (GS 3 ) geo site has a lower aesthetic value in spite of the breathtaking pano ramic view, plenty of easy accessible pathways and viewpoints and contrasting colour with the surrounding nature. The geosite Devil's Town (GS 1 ) is of exceptional scenic/aesthetic value re garding nature and its vicinity. The lowest value is ascribed to its spatial distribution in comparison with the area of other geosites (GS 4 and GS 3 ). The lowest aesthetic value within the analyzed geosites relates to the Sand pyramids (GS 2 ) due to a smaller area and a lesser number of landscape areas.
Considering protection, which is a very important indicator of the main values, only small differences were noted between these four geosites. The lowest level of protection goes to the Sand pyramids (1.31). Some higher values were exhibited at Dev il's Town (1.80) and the Stob pyramids (1.90). The geolocality Melnik is reasonably the highest ranked (2.09) as it has been un der protection much longer than the other three geosites. The big gest differences among the subindicators were recorded for the level of protection and accommodation capacities. The largest areas are occupied by the geosites Melnik (GS 4 ) and Stob (GS 3 ), hence their values are the highest. In contrast, the geolocality Sand pyramids (GS 2 ) covers the smallest area and thus displays the lowest value.
Considering the additional values, particularly the natural and anthropogenic ones, the best results were indicated by the geosite Melnik (GS 4 ). Being wellknown for its natural values and surrounding settlements of rich culturalhistorical heritage, Melnik (GS 4 ) displays the highest additional, natural and anthro pogenic values. Stob pyramids (GS 3 ) are also surrounded by plenty of natural and anthropogenic values, whereas the remain ing two geosites (GS 1 and GS 2 ) are less worthy due to their dis tance from other attractive tourist destinations. The vicinity of emissive centers is among the functional values of the lowest value in all of the analyzed geosites. However, some higher valu es Melnik (GS 4 ), has the highest touristic value among the an alyzed geosites, being particularly noteworthy for its touristic infrastructure among the subindicators (designed long pedes trian pathways, resting places at viewpoints), hostelry and res taurant services placed next to the pyramids. However, the num ber of visitors is not in accordance with promotional activities, remaining insufficient and at a low level. Slightly lower touristic value displays Stob (GS 3 ), whereas the geosite Devil's Town (GS 1 ) remains far behind Melnik and Stob due to insufficient interpre tative panels, the distance from visitor centers and hostelry ser vices. The advantage of Devil's Town in comparison to the other analyzed localities is the significant level of promotional activi ties. The lowest touristic values exhibited by the Sand pyramids (GS 2 ) having low values of all the subindicators.
According to the final results for all the analyzed geosites, given in table 3, are the determined positions in MGAM matrix (Fig. 9).
On the basis of the final results (Table 3) it could be con cluded that in the future attention should be paid to the additional values at geosites GS 1 and GS 2 . Subindicators obtained low valu es due to the distance from broadcasting centres as well as visitor centres, and the geosite lacked accommodation services, interpretative boards and additional functional values. In addi tion to these elements, there is a high level of sensitivity of geo sites to natural and human interferences.
In spite of all the geotourist values that the site of the Dev il's Town has, the manager of AD "Planinka" from Kuršumlija must be ready for the development of competition in the wider area, while at the same time tightening the criteria for assessing the load on the environment. This company must improve the quality of the resulting solutions, innovate procedures and learn to continue the improvement of activities and successful achieve ment in competitive surroundings (SÜTŐOVÁ et al., 2018).

SUMMARY AND CONCLUSION
It could be concluded that the highest differences within the ana lyzed geolocalities display touristic values that rely on tourism development in the country where the geosite is located and on tourist valorization of geosites. Subindicators from this group, such as promotion, organized visits, interpretative panels, tour ism infrastructure, guidelines, accommodation and restaurant services, could be easily changed and improved by human activi ty and investment in tourism development.
According to the position of the evaluated geosites in the GEM matrix, along with the final results presented in Tables 2 and 3, the absolute domination of Melnik (GS 4 ) among the ana lyzed geosites is apparent. However, the inevitable upgrading of additional values for a better position in the matrix is necessary.
The Sand pyramids (GS 2 ) occupy the lowest position in the matrix, having significant main values, but unfortunately display ing the lowest additional values. This suggests the high potential of the Sand pyramids and direct progress in geotourism develop ment with the improvement of additional values, particularly touristic ones.
Devil's Town (GS 1 ) is most similar to the Stob pyramids (GS 2 ) regarding the main values. Concerning the additional valu es, both geosites belong to the moderate level. Nevertheless, the Stob pyramids occupy a higher position in the matrix due to higher additional values. Thus, the appropriate increase of func tional and touristic values would contribute to a better position in matrix.
Furthermore, the management of each geosite should focus on a specific market segment shaping and directing the develop ment of the site towards the specific needs and preferences of tourism segments. Therefore, this research indicates what is im portant for the different segments when visiting a geosite so it can be used as a framework for tourism planning. Having said this, the management of each geosite should develop a tourism strate gy depending on whether it intends to become a destination for mass tourism or to attract smaller specific tourism segments such as pure geotourists and thus base the development of a geosite ac cording to their needs and preferences. In order to strike the right balance between the offer for general tourists and pure geotourists in the future, we should keep tourism development in a sustainable form, taking care of the protection of geosites and reducing the negative impact of tourism, which can be triggered by mass tourist visits.