Thought to be the biggest single-chamber cavern in the state, Devil’s Sinkhole is a massive vertical cavern with a total depth of over 350 feet. Most people don’t visit Devil’s Sinkhole to see the hole, itself—they come for the bats. This cavern, part of the Edwards Plateau in the Hill Country region of Texas, serves as the home to one of Texas’s largest colonies of Mexican free-tailed bats. The bats come seasonally and from the end of spring in to early fall, about 3 million of these creatures reside in this cave. You can’t go into the sinkhole itself, but there is a viewing platform that stretches over it, allowing you to peer down into the dark cavern below.