Weimer Lake, in Wapehani Park (Bloomington, IN) has a sinkhole on its southern side, which sometimes opens and sometimes closes. This year, the sinkhole is side of a large car, and the lake water drains through it pretty fast.
This sinkhole has been mostly open for the last 2-3 years. The City of Bloomington's plan for dealing with the problem? Demolish the dam and drain the lake!