Kaali is a group of 9 meteorite craters in the village of Kaali on the Estonian island of Saaremaa. Most recent estimates put its formation shortly after 1530–1450 BC (3237+/-10 14C yr BP). It was created by an impact event and is one of the few impact events that has occurred in a populated area (other ones are: Henbury craters and Carancas crater). Before the 1930s there were several hypotheses about the origin of the crater, including theories involving vulcanism and karst processes. Its meteoritic origins were first conclusively demonstrated by Ivan Reinvald in 1928, 1933 and 1937.

Source: Wikipedia