Inner Space Caverns: Mysterious Beauty Beneath the Interstate

Discovered in 1963 by a core drilling team of the Texas Highway Department as they planned construction of Interstate Highway 35, Inner Space Caverns, known as Laubach Cave to paleontologists, is one of the best preserved caves in the state.

Nearly 70 feet beneath the busy freeway, Inner Space Caverns displays its long-hidden treasures, mystifying and delighting locals and tourists. Visitors are routinely amazed at the up-close views of exquisite stalactite and stalagmite formations, among the other geological wonders.

Visitors Discover That Rocks Rock!

The underground secret opened to the public as a “show cave” in 1966. Dynamite blasts created the main entrance, while one of the original Highway Department 18-inch holes now functions as an emergency exit and ventilation port. The first room the crew discovered is known as Discovery Cave, or the Outer Cathedral. Visitors can still see the hole through which the first brave explorer entered, and remarkably beautiful calcite walls glow with orange and pink.

Created by the slowly evolving artistry of water and ice, the caverns offer diverse examples of formations: each cubic inch represents 100 years of growth! Other highlights of the tour include a white flowstone, known as “The Flowing Stone of Time”; Bone Sink, with its crumbling mammoth tusk; the Inner Cathedral; Soda Straw Balcony; Lake of the Moon and Lunar Landscape. Occasionally the caverns do flood, which requires closure of the trail.

Sightseer or Spelunker?

Estimated to be 90-100 million years old, the caverns did have natural openings that sealed shut about 14,000 years ago. Though several miles of passages have been explored, many sections remain a mystery, blocked by fill-ins and collapses.

Areas that have been explored and made available to the public offer a dazzling display of the incredible workings of Mother Nature and the delightful surprises of our amazing Earth. The spectacular caverns beckon at a constant temperature of 72 degrees and 98 percent humidity. Be sure to wear sturdy walking shoes — the pathways can be slippery! Most visitors opt for the general guided tour, but a more demanding spelunking adventure is available — if you don’t mind tight spaces and getting dirty.

The Geological Background of Inner Space Caverns

The Inner Space Caverns are examples of karst caves, produced by the dissolving action of acidic underground water on limestone. The result is the formation of caves, underground tubes, sinkholes and a rough land surface. The word “karst” stems from the German word, kras, which means “barren land,” and is the name for a region in Italy and Slovenia, the Kras Plateau.

Texas has many regions of karst that cover about 20 percent of the state. As a result, a minimum of 9,500 caves, sinkholes and springs are distributed throughout these areas. Because they channel water underground, the caves and aquifers are important for many purposes, including economic.

Believe it or not, Central Texas was cool and moist until about 3,000 years ago. As a result, moles and gophers were common and their remains have also been discovered. Today the only vertebrate animals in the caverns, other than astonished visitors, are tiny tricolor bats. The caverns are home to many invertebrates, however, including two endangered species, the Coffin Cave mold beetle and the Bone Cave harvestman (an arachnid).

The Oldest Prehistoric Remains and Fossils in Texas

Inner Space Caverns is one of the few places in the state where remains of large prehistoric animals have been discovered. In fact, Inner Space Caverns is the origin of the oldest radiocarbon-dated bone ever found in a Texas cave. Dated over 23,000 years ago, the bones belonged to Platygonus compressus, an extinct peccary that frequently crawled into cave openings to die.

Significant vertebrate animal fossils have been found in only about 25 Texas caves. The animals may have fallen in and become trapped, while others drowned in a quicksand-type mud in the bottom of water holes. Some were dragged into the caves to be eaten. Fossils have included remains of extinct species, like the spectacled bear, flat-headed peccary, dire wolf, ground sloth, Columbian mammoth, huge bats, camel, horse, the scimitar- and saber-toothed cat, and glyptodont, a giant armadillo.

More Than Just Another Roadside Attraction

Described by visitors as “gorgeous,” “exhilarating” and “spooky,” the Inner Space Caverns are more than just another roadside tourist attraction. This beautiful treasure is a reminder of our intimate connection with the earth, the past and with time itself.