Early on, Issyk Kul also drew attention from researchers for the remains that lie beneath its stunning cobalt waters. It's an endorheic lake (meaning that it has no outlet) with abundant underwater springs, and the water level has fluctuated dramatically over the centuries, submerging settlements, buildings and even entire cities that had been established on earlier shorelines. Issyk Kul was one of the earliest sites for underwater archaeological research in Central Asia, with divers exploring its depths as long ago as the 1860s. In the Middle Ages, the region around the lake was hotly contested by two divergent lines of...