The volcanic Crater lake is U-shaped, surrounding Mount Gharat on all sides except southwest. It is about 9 km long (north to south) and about 6 km wide, with an area of 19 km². It is situated in the center of the 20 km diameter island; the lake rests 418 meters above sea level and it is 119 meters deep. It is a fresh water lake with a temperature of 32° Celsius, where only eels and shrimps can survive. The water in the lake is not very clear, but has a greenish color. Water constantly flows out of the lake at a natural overflow located on the eastern side of the lake. The water flows about 3 km east to Siri Waterfall and then another 3 km through rivers Namang or Be Solomul before it reaches the sea.