Wyandotte Caves

Wyandotte Caves are a pair of limestone caves on the Ohio River in Crawford County, Indiana, northeast of Leavenworth, inside O'Bannon Woods State Park. They were designated a National Natural Landmark in 1972. The name covers two separate caves: Wyandotte Cave, called the Historic Cave, and Little Wyandotte Cave, also known as Siberts Cave.

Wyandotte Cave has about 9.2 miles of passages on five levels, long open corridors and large rooms. Monument Mountain, 135 feet tall, is considered the world's largest underground mountain, and the cave also has many rare helictites. Little Wyandotte is smaller and wetter, with flowstone, stalactites, columns, soda straws and banded flowstone known as cave bacon. Both caves stay at a constant 52 °F.

Native Americans used Wyandotte Cave for nearly 4,000 years, lighting it with torches of hickory bark and grapevine to mine aragonite and chert, which they made into ornaments and stone tools. Traces of that mining can still be seen. European settlers are believed to have found the cave around 1798. It became a source of saltpeter, a component of gunpowder, which peaked during the War of 1812, and the cave also yielded Epsom salts. Tours still pass the vats and hoppers used in that work.

The first commercial tours began in 1850, which makes Wyandotte one of the oldest commercial caves in the country. The state bought the caves in 1966. They closed to visitors from 2009 to 2016 to slow white-nose syndrome among the bats, and today they shelter more than 30,000 bats of nine species, including the endangered Indiana bat.