Inner Space Cavern

Click on Map below for a larger image

  • Location: Georgetown, Williamson County
  • Length: 6114.7m (20,061 ft)
  • Depth: 21m (69 ft)
  • Contact: Website for tour details and hours
  • Other Information: Facebook Page
  • Other Amenities: Country store, candle factory nearby. Downtown historical district 3 miles away.


Head north from Austin on IH 35 for about 27 miles to Exit 289 onto Business 81 to Georgetown. Turn left under the overpass and cross the railroad tracks on the west side to the cave headquarters. The cave actually goes under the Interstate highway.


Inner Space Cavern is a large, complex cave with many beautiful formations and interesting displays of Pleistocene-age mammal bones.

Known to paleontologists as Laubach Cave, Inner Space was discovered in 1963 when boreholes were drilled to test for a highway overpass on IH 35. A cavity was repeatedly found at about 10 m (33 ft.), and a 36-inch corehole was drilled to investigate. A highway engineer was lowered on the drill stem into what is now called the "Outer Cathedral." The Highway Department soon allowed exploration by the Texas Speleological Association, and about 2.1 km of passage were mapped. The cave was sealed, and the freeway was completed.

In 1964 the Georgetown Corporation was formed and leased the cave from the Laubach family, who retained the right to use the cave. They soon excavated a sloping shaft into the west side of the cave with the help of cavers. The cave was opened to the public as a show cave in 1966. Visitors enter the cave on a cable car ride. The trail, about 550 m (1,800 ft.) long, is smooth and sloping, admitting even wheelchairs. At first the trail passes through trenches cut into the floor, but soon it enters the large Outer Cathedral, where one can see the corehole where the first explorer entered. A beautiful white flowstone, The Flowing Stone of Time, can be seen with water flowing over its flanks. The tour then passes under a high ceiling with large scallops and pendants, past the talus cone of Bone Sink, where a crumbling mammoth tusk is visible, to the Inner Cathedral. The tour then stops at the Lake of the Moon for a dreamy sound-and-light show, then moves on to the Lunar Landscape, which examines another side of the bone sink. The tour then retraces its route to the entrance. A religious son et lumiere show is presented at The Flowing Stone of Time.

Inner Space is a complex floodwater maze superimposed on an ancient trunk passage system. The cave is generally oriented north-south and consists of large passages and rooms interconnected by smaller passages, the latter probably of more recent origin. The cave occasionally floods with clear, phreatic waters, closing part of the trail for months. "The Volcano" is an interesting feature in the off-trail area; it is a mud crater about ½ m across in the corner of a room. The Volcano probably was formed by water welling up out of the floor. A large, plugged sink nearby could provide the necessary hydrostatic pressure after a heavy rain.

Inner Space is one of the leading Pleistocene paleontological sites in Texas. Several sinkhole entrances were open to the surface about 13,000 to 25,000 years ago, as evidenced by dated remains of extinct mammoth, saber-toothed cat, glyptodont (a Volkswagen-sized armadillo), camel, horse, ground sloth, short-faced bear, peccary, bat, and other species. The oldest radiocarbon-dated bone from a Texas cave came from Inner Space -23,230 ± 490 years before present. The cave contained several complete skeletons of Platygonus compressus, an extinct peccary. This species had a habit of crawling into remote passageways to die.

Exploration is not complete but has been slowed by breakdown areas that are difficult to excavate. A resurvey of the cave seems to have bogged down.

The cave contains a diverse invertebrate fauna, including two endangered species, Texella reyesi (Bone Cave harvestman) and Batrisodes texanus (Coffin Cave mold beetle).


Elliott, W. R. 1970. Inner Space Cavern-Third longest cave in Texas. Texas Caver, 15:203-211.

Elliott, W. R., and L. O'Donnell. 1993. Draft recovery plan for endangered karst invertebrates in Travis and Williamson counties, Texas. U.S. Fish & Wildlife Service, Albuquerque, New Mexico.

Kastning, E. H., Jr. 1983. Geomorphology and hydrogeology of the Edwards Plateau karst, central Texas. Ph.D. dissertation, Univ. Texas, Austin, xxxi + 656 pp. + 6 pl.

Reddell, J. R., and W. R. Elliott. 1991. Distribution of endangered karst invertebrates in the Georgetown area, Williamson County, Texas. Report to City of Georgetown. 64 pp.

Russell, W. H. 1980. Inner Space: Exploration of the dry section. Texas Caver, 25:101-103.

All data on this page and on the linked Show Caves is revised from:
William R. Elliott and George Veni (eds.). 1994.
The Caves and Karst of Texas: 1994 Convention Guidebook.
Natl. Speleol. Soc., Huntsville, Alabama.
352 pp. + viii + 13 maps. All rights reserved.
Original page by William R. Elliott