Tyson Spring Cave in southeastern Minnesota is a long karst cave in the Driftless Area, with most of its passages about 120 feet underground and an estimated mapped length of 3.5 to 5 miles. After decades when explorers could go only about 800 feet before reaching a flooded passage, work in the 1980s opened access to deeper sections and eventually allowed non-divers to explore the known system. In 2006 the Minnesota Cave Preserve secured the land and improved controlled access. The cave is especially significant for Ice Age fossils, including Minnesota’s first recorded stag-moose and the Great Lakes region’s first recorded saber-tooth cat, along with more than 175 extinct animal bones.