Blue Hole

Blue Hole in Castalia, Ohio, is a freshwater cenote formed as a water-filled sinkhole in limestone country and long known for its striking clarity, vivid blue color, and nearly circular basin. Known to Native Americans and first recorded in 1760, it became a major roadside attraction from the 1920s to 1990, drawing up to 165,000 visitors annually. Though once thought bottomless, it is about 43 to 45 feet deep. Fed by an underground stream, its mineral-rich water remains near 48 °F year-round and changes little with floods or droughts. Because the pond is anoxic, it cannot naturally support fish.

Castalia, Ohio · United States