Wonder Cave is a natural cavern in the Purgatory Creek system on the Balcones Escarpment in southern Hays County (at 29°53' N, 97°57' W). Its entrance is one mile southwest of the county courthouse in San Marcos. The cave is reported to be the only commercially operated dry-formed cave in the United States-"dry-formed" because the fissure was opened not by erosion but by the earthquake that produced the Balcones Fault. The fault line itself is visible in the cave's ceiling. Originally named Beaver Cave after Mark Beaver, who discovered it in 1896, the cave for a while concealed Beaver's illicit distilling and gambling enterprises. In recent years it has become part of an amusement park that features tours of the multichambered cave and a wildlife park.