Inner Space Cavern

Inner Space Cavern, a large commercial cave near Georgetown, Williamson County, was discovered by the Texas Highway Department (see TEXAS DEPARTMENT OF TRANSPORTATION) during drilling to test underpass foundations in May 1963. Early exploration by Texas spelunkers was permitted by way of a large-diameter hole drilled into the roof of one of the cave's rooms. The present entrance is an artificial tunnel equipped with a cable car. Inner Space is situated in Edwards Limestone (Mesozoic Era) and is estimated to be sixty to 100 million years old. Geologists attribute formation of the cave to the action of underwater currents when the Permian Sea covered the area. Ninety-five percent of the highly decorated and complex cave is still active. A large variety of vertebrate fossils of the late Pleistocene age were recovered from two entrances to the cave, which have since been filled.