Devil’s Den, in Florida, is an underground spring inside a cave that got its name from early settlers, who thought the steam rising from the Earth looked like it was coming from hell.

Now, the collapsed river bed has become a popular spot to scuba dive and snorkel while being surrounded by ancient rock formations and fossil beds.

Some of the fossils in Devil’s Den date back to the Pleistocene Age, and as old as 33 million years. Fossils of mastodons, ground sloths, and even sabre-toothed cats have been found in the spring — and many of the fossils are now on display at the Florida Museum of Natural History, at the University of Florida.

One of the best parts of the Devil’s Den is heading underwater with your scuba and snorkel gear and exploring the warm, clear, 72-degree waters.

Once you’re done exploring, the site also has picnic tables and a food truck, in case you’ve worked up an appetite.

And if you’re worried that such a prehistoric site is hard to get to, have no fear. It’s located in Willeston, Florida, about a 30-minute drive from Gainesville. Lodging options include hotels and camping.