There's a lake that's a giant sinkhole - Apparently.
Lake Matano, located in Indonesia, is a 23-kilometer-long lake that's actually a massive sinkhole. It's estimated to be over 900 meters deep, making it one of the deepest lakes in the world. The lake's unique geology is due to the fact that it's a remnant of an ancient riverbed that was carved out by erosion. Despite its massive size, the lake is relatively shallow in some areas, and its water level is controlled by a narrow outlet at the lake's bottom. This natural wonder is a fascinating example of the Earth's geological history.