No Swimming!

 

Kawah Putih lake is one of the two craters which make up Mount Patuha , a stratovolcano.  Kawah Putih crater lake is a stable volcanic system with no records of significant activity since around 1600.
The lake is almost 8,000 feet above sea level and temperatures hover around 50 degrees. Kawah Putih is an extremely acid lake (pH 0.5-1.3) which changes colour from bluish to whitish green, or brown, depending on the concentration of sulfur and the temperature or the oxidation state.
There was formerly a sulfur mine at the crater although production has now ceased have has been open to visitors since 1987.  Today it's a tourist destination :)!