Inner Space Cavern
This Mesozoic-era karst cavern 24 miles north of Austin was discovered in 1963 and opened to the public three years later. Visitors enter from a 1¼-mile hiking path. Tours vary in length from just a little more than an hour to nearly four hours, the latter not suitable for kids under 13. The temperature is a year-round 72°. Sometimes there are $1 coupons on the website.
