Inner Space Cavern

By: A. Richard Smith

Type: General Entry

Published: 1976

Updated: April 4, 2019

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.

Don Adams, "Inner Space," Texas Parade, October 1966. Tommie Pinkard, "Under the Interstate," Texas Highways, May 1966. Jerry and Dorothy Sinise, Texas Show Caves (Austin: Eakin Press, 1983).

The following, adapted from the Chicago Manual of Style, 15th edition, is the preferred citation for this entry.

A. Richard Smith, “Inner Space Cavern,” Handbook of Texas Online, accessed July 06, 2022,

Published by the Texas State Historical Association.

April 4, 2019