This is a crater lake which is quite acid (pH 0.5-1.3!) from sulfur dissolved in the water. The water has a striking bluish to greenish color and there is a strong sulfur smell all around. Wikipedia
Fumaroles and bleached rocks
Milky colored water
A little girl dipping her hand in the water
Although inactive, there must have been some changes since those trees died.
Popular place for young couples to date...
... and kids to play!
The external side of the crater is the site of luxuriant forest !