Lake Issyk-kul, Kygyzstan
1600m above sea level.

Approximately 110 km long, 65 km wide and 700m deep. It is the second largest alpine lake in the world after Lake Titicaca in South America.

Although at such high altitude, it does not freeze over during winter due to the thermal activity in the area and it's slightly saline composition.

Lake Issyk-kul was used during the cold-war as a Soviet torpedo testing range.