Hanging Rock and Wabash Reef National Natural Landmark is a 400 million year old  limestone deposit coral reef formation that has a hanging appearance; it has been designated as a National Natural Landmark, and it is open to the public,
The site, located on the southern bank of the Wabash River near the town of Lagro, contains an impressive natural exposure of fossilized coral reef dating from the Silurian Period some 400 million years ago. The limestone reef deposit rises 75 feet (23 m) above the river and is being undercut by it, giving the site its "hanging" appearance. Hanging Rock is owned by Acres Land Trust, and is open to the public from sunrise to sunset. 1986 
