Lake Natron, Tanzania
This lake has a uniquely high salt content. Salt-loving microorganisms thrive and produce red pigment, colorizing the water. For other animals, the salt is deadly and many calcify (effectively turning into stone) after taking a dip in the water.
Sadly, the mining company that owns the caves could no longer afford to keep the massive pumps going to clear the chamber. I believe the pumps were shut down a few years ago and the cavern is refilled with water. The crystals are growing once again, but no one will ever see it.