Inner Space Cavern

Useful Information

Funicular at the cave entrance.
Photographer: Knut Brenndörfer
Photographer: Knut Brenndörfer
A gour.
Photographer: Knut Brenndörfer
Location: Beneath the I-35, 38 km north of Austin. Exit 259 Georgetown, on the West side of the freeway, right on the access road.
Navi: 4200 S. I-35 Frontage Rd., Georgetown, TX 78626
(30.60809376162819, -97.68812567341357)
Open: All year Mon-Fri 9-16, Sat, Sun, Hol 10-17.
Closed Thanksgiving, 24-DEC, 25-DEC, Easter.
Fee: Adventure Tour:
Mon-Thu Adults USD 20.95, Children (4-12) USD 14.95, Children (0-3) free.
Fri-Sun, Hol Adults USD 21.95, Children (4-12) USD 15.95, Children (0-3) free.
Groups (20+): Adults USD 14.78, Children (4-12) SEP-FEB USD 6, MAR-MAY USD 6.50, JUN-AUG USD 9, reservation mandatory.
Hidden Passages Tour:
Mon-Thu Adults USD 25.95, Children (7-12) USD 17.95, Children (0-6) not allowed.
Fri-Sun, Hol Adults USD 26.95, Children (7-12) USD 18.95, Children (0-6) not allowed.
Combo Adventure Tour/Hidden Passages Tour:
Per Person Discount USD 4.
Wild Cave Tour:
Per Person USD 100.
Classification: SpeleologyKarst Cave
Light: LightIncandescent Electric Light System
Dimension: T=22 °C, H=98%, L=6,400 m.
Guided tours: Adventure Tour: L=1,600 m, D=75 min.
Hidden Passages Tour: L=1,600 m, D=75 min, MinAge=7.
Wild Cave Tour: D=4 h, MinAge=13.
Photography: allowed without tripod
Accessibility: no
Address: Inner Space Cavern, 4200 S IH 35 Frontage Rd, Georgetown, TX 78626, Tel. +1-512-931-2283. E-mail:
As far as we know this information was accurate when it was published (see years in brackets), but may have changed since then.
Please check rates and details directly with the companies in question if you need more recent info.


Spring 1963 discovered by a Highway Department crew drilling core holes for an overpass of a new highway.
NOV-1963 first exploration by the Texas Speleological Society.
Summer 1966 opened to the public.


Organ pipe flowstone.
Photographer: Knut Brenndörfer
Speleothems in a cleft.
Photographer: Knut Brenndörfer

Inner Space Cavern is entered with a cable car, called Scenic Subway. This cable car is a funicular, where a railroad wagon is hanging on a rope and lowered by a winch. This cave has numerous nice speleothems, including gours, rimstone pools and helictites.

The cave was discovered during road works in Spring 1963. A Texas Highway Department core drilling team was taking six inch (15.24cm) core samples to determine if the ground was stable enough to support a large highway overpass. One time, at a depth of 12 m, the bit suddenly dropped more than eight meters. The news spread and the Texas Speleological Society secured permission to enter and explore the cave. The 15 cm hole is to narrow for a person, so the widened the hole with a bigger bit and finally the first group of speleologists from the Texas Speleological Society entered the cave on a cool November morning in 1963. They were lowered on a rope from a wooden tripod, which was erected over the core hole. The rope was lowered and pulled by a car. During this first exploration in a few days 2,133 m of cave passage were explored and surveyed.

There are three tours offered, the normal show cave tour which is called Adventure Tour, the Hidden Passages Tour which is more or less a walking tour through unlit and unpaved parts of the cave, and the Wild Cave Tour which is a three hour cave trekking tour. The regular tour is for the average tourist and you only need a sweater and walking shoes to participate. The trails are paved and electrically lit. The Hidden Passages Tour is a sort of cave stroll, leading through an unlit but level passage, it is simply walking on level trails on the natural cave floor. There are some narrow passages and large, uneven steps. Lamps are provided. The Wild Cave Tour takes up to four hours, and is a true cave trekking tour. Participants get full caving gear and must stoop and crawl at various points. Minimum age is 13.