Klyuchevoye Lake is located in the caldera of Ksudach Volcano. It is part of South Kamchatka Nature Park which is included in the UNESCO World Cultural and Natural Heritage List.
In the caldera is the Shtyubel cone. On March 28, 1907 an important eruption resulted in the collapse of its crater. It then filled with water thus creating lakes Klyuchevoye and Shtyubel. Klyuchevoye is fed by Shtyubel, which is 2 km away.
Klyuchevoye Lake covers an area of 8 square kilometers. The lake is 4km long and 2 km wide. It is encircled with walls from 400 to 500 meters high. It is 96 meters deep. The temperature at the bottom of the lake is 40°C. It is 20% thermal water and is lightly alkaline and mineralized.