Spaces under elevated highway tracks are likely to be given negative images as dark, dirty, and low security spaces. So people tend to stay away from that kind of spaces. Nowadays, people recognize the Metropolitan Expressway (ME) as the negative heritage of rapid economic growth while its underneath spaces are still undeveloped. Therefore, this study tried to make clear the actual condition how people use a play lot built under the ME, on the basis of a survey on existing land use of underneath spaces of the ME along the tracks. Comparing to the ordinary play lot adjacent to the under-ME play lot, play activities were examined by observation, and accesses, frequency of using, staying time and evaluation for the play lot were examined by Questionnaires. As a result, it was observed that a under-ME play lot has some significance as “nitch” spaces where indoors-type activities like card games were remarkable. It can be said that some planning theories dealing with such kinds of usages of play lots or public parks are further needed in highly dense and sterically developed urban environments.