1.Introduction
1.1.Background and purposeTokyo, the largest agglomeration in the world was once a garden city 1) , abundant in waterways, but due to environmental and land reclamation concerns, most of the medium and small-scale streams were culverted in the middle 20th century. As a result of strong globalization influences the city has dramatically lost its connection to nature and water, but the memory of its extensive water network is still present in the shape of pedestrian green-streets, that wind through the cityscapes. They are highly valued and utilized by the populace. Those corridors form a network spreading throughout Tokyo and enhance the living conditions on a neighborhood level and for the city. There is a growing number of literatures 2) 3) 4) 5) 6) and enthusiasts who are exploring the subject of the 'hidden' waterways in the city. Yet, most of the books deal with matters such as topography, mapping and hints on how to detect a hidden river, but their urban quality and meaning as walkable infrastructure is yet to be realized. Therefore, this study's aim is to add more qualitative knowledge to the exploration of those public elements. To assess the quality of the public space there are loads of techniques to choose from. A practical technique should be measuring the right set of conditions that creates a good public space. One such empirical method successfully applied on different cases 7)8) of public space is Mehta's (2007) Good Public Space Index (GPSI) 9) . Recent research on public space quality assessment tools acknowledged the UN-Habitat and GPSI tools as the ones that "covers most aspects of human needs and are thus considered to be the most comprehensive" 10) .Likewise, this research acknowledges and utilizes the GPSI method and applies it on three cases of covered waterways in Tokyo Metropolitan Area, with different characteristics of use and urban design. Based on the fieldwork observations, this research hypothesis is that the busiest case, Kuhonbutsu Promenade, would perform better than the rest.The purpose of this study is to verify those assumptions by using scientific evaluation method to compare and rank the urban space performance of each type of case. Understanding the meaning of the public spaces created on top of culverts as an urban common can serve as a significant groundwork for future advancements in city planning practices.
