Spelunking in Austin

Inner Space Cavern. This Mesozoic-era karst cavern 24 mi north of Austin was discovered in 1963 and opened to the public three years later. Visitors access the entrance via cable car and can choose from two trails, one that is.75 mi and another that's 1.2 mi. Tours vary in length (and price), from just a little over an hour to nearly four hours. The temperature is a year-round 72°. Kids get discounted admission; the three- to four-hour tour is for ages 13 and older only. On Saturdays, reservations are required and groups can be no larger than four. Sometimes there are $1 coupons on the Web site. 4200 S. I-35, Georgetown. 512/931-2283. www.innerspace.com. $15-$100 depending on tour. Mid-May-early Sept., daily 9-6; early Sept.-mid-May, Mon.-Fri. 9-4, Sat.-Sun. 10-5.