The Cave of the Mounds found on the south slope of the eastern hill of Blue Mounds, Wisconsin is known to be the ?jewel box? of all American caves and a National Natural Landmark. This is because of the ?speleothems?, which are various mineral formations found inside the cave. Its opening was accidentally blasted off by some miners in 1939, thus the 20-feet high natural limestone cavern was revealed. It is believed that the limestone that makes up the cave started forming in about 488 million years ago.

The Cave of Mounds was initially closed to protect it from the curious people who came to see it. But soon enough, it was developed to accommodate millions of visitors by installing concrete walkways and lighting inside the cave, while picnic spots, walking trails, gardens, a visitor center and gift shop was opened to enhance the cave?s tourist appeal.