Wonder World Park

"They ran back down here and turned on all the lights, and I came shooting out," he said.

Wonder Cave formed during an earthquake an estimated 65 million years ago and has drawn millions of tourists since opening to the public in 1900.

Mostyn took over the family business in 1972 after graduating from Texas State University. He said the cave is known throughout the world because it is the only place where a person can travel underground to see the effects of an earthquake along a fault zone—in this case, the Balcones Fault where the Texas Hill Country jams into the Gulf Coastal Plains.

"You'll get to see first-hand how the earth was ripped apart and big giant boulders caught in mid-air as they were falling," he said. "When you study earthquakes and tectonic plate movements, there's nothing better than seeing first-hand the actual result of an earthquake."

Mostyn said Wonder Cave is the only commercial cave in Texas not formed by water erosion. The tour begins from a gift shop, descends into several narrow passageways and larger chasms where the air cools to 70 degrees year round, and ends at an elevator.

"When you exit the cave, we take you 110 feet above the ground surface to the observation tower, so you can look down at the major breakoff point of the Balcones Escarpment," he said. "You're right on top of it. From there, you can actually see how the earth's surface changes drastically right at this fault line."

The park also features a train ride from which guests can feed deer at a wildlife park featuring more than 100 animals such as llamas, goats, guineafowl and turkeys.

Mostyn said attendance is growing at the park. In 2011, Wonder World hosted 125,000 visitors during the summer busy season, and more than 2,000 school groups have come through in 2013.

"What's happened is that Central Texas has become a destination for floating, camping, and everybody helps everybody draw to this area," he said. "We're in the corridor of where all of it's happening, so it's kind of a no-brainer, really. We have to keep our heads straight and keep right out there in front of the public, and we definitely have been growing because of it."

Wonder World Park, 1000 Prospect St., San Marcos, 512-392-6711, www.wonderworldpark.com, Hours: Every day 8 a.m.–8 p.m. in summer, Mon.-Fri. 9 a.m.–5 p.m., Sat.-Sun. 9 a.m.–6 p.m. September–May, Tickets: $22.95 (ages 13 and older), $15.95 (ages 6–12), $8.50 (ages 3–5), free (2 and younger)