Olentangy Indian Caverns in Delaware, Ohio, is a three-level limestone cave system formed millions of years ago by an underground river. Before it became a seasonal attraction, the Wyandotte used its caves and passages as refuge from severe weather and from enemies identified here as the Delaware Indians. Artifacts indicate Wyandotte use as late as 1810, linking the site directly to Native history in the region. The caverns were rediscovered in 1821 by J. M. Adams, whose carved initials remain at the entrance. With many openings and passages still not fully explored, the site is significant for both its geology and its long human use.