The Hasankeyf Antique City located in southeastern Anatolia (Turkey) includes several historical heritages and man-made caves. It is mainly located in dolomitic limestone. The city will be partly under water after reservoir impounding of the Ilisu dam, and the limestone will be subjected to cyclic processes such as wetting-drying and freezing-thawing. Although a new town is formed and part of the city is transported to a nearby area, this cannot be done for many existing historical and cultural values at the site. The behavior of the limestone under cyclic processes is not known. In this study, deterioration mechanisms of the limestone were investigated with field and laboratory studies. It is found that the rock is not durable. Very thin surficial deterioration zone exists on the rock surface. Discontinuity-controlled block failures associated with collapse of man-made caves occur at the site before reservoir impounding. Further discontinuity-controlled block failures are expected to occur after reservoir impounding by aggravated deterioration and surface erosion of the rock within the fluctuation zone of the reservoir.