Spring Mill State Park, established in 1927 near Mitchell, Indiana, combines the limestone cave and sinkhole landscape of the Mitchell Karst Plain with historic preservation and recreation. Its caves include Twin Caves, Bronson Cave, Shawnee Cave, also called Donaldson Cave, and Hamer Cave, and Twin Caves features a boat tour underground. The park also protects virgin timber in Donaldson Woods Nature Preserve. Its best-known historic feature is a reconstructed pioneer village on the site of old Spring Mill Village, centered on a watermill and other historic structures. Much of the park’s present layout, including the inn, lake, and trails, was created by the Civilian Conservation Corps in the 1930s.