In this paper, the water distribution system at the Upper city of a well-preserved medieval town of Hasankeyf near the Tigris is questioned and its relation to the urban settlement pattern is assessed. The discussions are based on the cistern-intensive and available canal data collected within the residential borders of the Upper city in 2005. Being the third level features of the water system, the cisterns the majority of which are now attributable to the "conical, small and individual" typology, have shown that they were actively operated through the open rock-cut canals which were fed by the backbone of the distribution network-namely the siphon system, until recent times. Although a considerable number of converted cisterns hallmark shifts in the function of the water system and the changing conjectures over time, the blue prints of such a big "hydro-design" reveal the competence of semi-arid occupational environments in Upper Mesopotamia in showing how to cope with the topographical constraints and climatic disadvantages and turn these into an opportunity through the efficient use of terrain along with a carefully designed settlement area. That the Upper city now offers numerous water features makes this piece of land quite a representative of the regional works and shows the apex of the perception of ancient technology achieved with the siphon that could have been launched in the Roman era, and the state of art of planning ancient natural and man-made habitats.