Earlier this spring, I visited Austin with my family, and one of our day trips from the city took us to the Inner Space Cavern in quaint Georgetown. Only 25 miles north of Austin and right on Interstate 35, the cavern is easy to reach and offers something for everyone.
After being discovered in 1963, the cave opened commercially in 1966 and now offers three different guided tours for visitors. The most popular “Adventure Tour” lasts about an hour while a guide leads the group on a paved, lit trail through the largest rooms. The “Hidden Passages Tour” offers a closer look at the cave and its passages. Groups are much smaller, and guests carry their own flashlights while a guide leads them along an undeveloped trail through often narrow passages and some larger rooms. But the hardest, most adventurous “Wild Cave Tour” is not for your everyday visitor. It’s 4 hours long and offers an adventure for spelunkers since it includes crawling through narrow and low passages.
We opted to take the Hidden Passages Tour for a more intimate look at the cave, its formations, and its passages.
The Hidden Passages Tour Offers A More Intimate Look At The Cave
Our guide, a retired science teacher, gathered our small group and gave us each our own lantern to carry through the cave. He explained we would walk through dark passages in the cave along an undeveloped, often uneven trail that is muddy in some places. The round trip would take us about 1.5 hours, he explained, and we would cover about a mile during that time.
The underground walk was an adventure and a great learning experience. Walking on the uneven surface, stepping in puddles or mud in some places, getting “cave-kissed” (drops of water landing on us), and seeing only as much as our flashlight allowed, we felt like explorers.
At one point, our guide had us all turn off our lights. That’s when we understood the real meaning of pitch dark. Outside a cave with the sky above, even on the darkest nights, you see some light from even the faintest stars. But underground, we experienced such true, pitch darkness, where we couldn’t even see our own hands near our eyes. You would need to rely on all your other senses if you were to be stranded without a light in a cave.
Then, before even having us turn on any of the lanterns, he shone his on the surrounding rocks. Some of them glowed under his light.
Exploring The Cave Offers Lessons Of Geology
One of the best-preserved caves in Texas, the Inner Space Cavern is a karst cave formed in the Edwards limestone of Texas. During the tour, we learned the cave was formed in the Mesozoic Era, between 60 to 100 million years ago, by underwater currents when the area was under the Permian Sea. Groundwater seeping through layers of the limestone continued the process over thousands of years. But limestone is not the only rock present in the cave.
As we walked deeper into the cavern, our guide pointed out different rocks. The difference between the rocks was most obvious when we turned our lights off, and he pointed his own UV light at different areas of the cavern walls and formations.
Some rocks were glowing in different colors, while others stayed dark. We learned about calcite and other fluorescent minerals of different colors that can temporarily absorb light. Some of them can hold on to it even after the light is turned off.
We witnessed this phenomenon, too, in the depths of the Inner Space Cavern. In fact, our guide was moving his light above some areas of the cave walls, “drawing” on them. After he turned off his light, we watched the rocks still emit light for a few seconds before our surroundings turned pitch dark once again, and we turned on our own lights to continue the tour.
… Also In Paleontology
Even before entering the cave, you’ll find a fossil display in the visitor center. Found in the cave, the fossils offer a history of the ancient animals that lived in the area.
When they started exploring the cave, paleontologists found fossils and bones of at least 44 different species, 11 of which are now extinct. Among these are the Colombian mammoth, giant ground sloth, saber-toothed cat, and an extinct pronghorn. However, as we found out later from our guide, the most common remains found belong to peccaries.
Inside the cave, the guide showed us several fossils of smaller creatures on the walls of the cave, right near the trail. They were easy to see if we knew where to shine our lights on.
You Can See Hibernating Bats Up-Close
Since we visited in early spring, we saw bats up-close still hibernating in the cave.
In fact, this cave is one of only a few places where we can see hibernating bats up close. We stopped several times when our guide pointed out a few, hanging from the cave’s ceiling or hidden in different formations.
One was even sleeping near the trail, so close that we could’ve touched him. Though I’ve seen bats before, this was the closest I ever came to one.
The bats of the Inner Space Cavern are the tiny tricolored bats (Perimyotis subflavus), earning their name with the three colors of the hairs on their back. They are one of the smallest bat species, known for their unusual tolerance of human activity nearby. However, the ones in these caves learned to be especially tolerant since everyone who enters the cave knows not to touch or harm them.
A 7-minute film about bats was playing in the visitor center, giving visitors the opportunity to learn about them even before entering the cave. The video explains facts about the tricolored bats of the cave and bats around the world.
… And Marvel At The Cave Formations
Stalactites, stalagmites, soda straws, and many other formations lined our path during the tour. Some of the soda straws even grew sideways, something I’ve never seen before in a cave. They seem to defy gravity, and scientists can only guess how they formed.
And while marveling at the stalactites, we learned they help scientists measure rainfall in any year. Like the tree rings above ground, the stalactites also have rings that show their growth related to rainfall. The thicker rings show more rainfall, while the thinner rings show less in the same time period.
We walked by openings to large rooms. Shining our light into them revealed more interesting formations like stalactites and stalagmites facing each other, some almost touching, others forming a column.
Other times, our guide pointed out narrow passageways the 4-hour-long tour would take; some of them looked like even when crawling, a person could barely fit through. Though I would not dare to do it, I could see why it would be fun for someone who loves caves.
While Learning About The Cave’s Interesting History
Hidden for 14,000 years, the Inner Space Cavern is now under Interstate 35 — during quiet moments, we could hear the rumble of the traffic on the road above. Though no one likes the busy highway above now, building it was the reason the cave became known.
As we learned on the tour, the Texas Highway Department core drilling team discovered it while building the road in the spring of 1963. While drilling to test for safety, their drill dropped, revealing the well-preserved natural cavern.
The Texas Speleological Society explored and mapped the cave, from tight passages to large, cathedral-like rooms. Besides several tight tunnels and the sticky mud, they found the cave safe and easy to walk through, so by 1966, they opened it to visitors.
Practical Things To Know When Visiting The Inner Space Cavern
Since it is a living cave, meaning it is still forming and changing, it is very important to remember not to touch the walls or any of the formations. Even the smallest cave formations take thousands of years to develop, and the oils on our skin would stop their growth; getting dirt on them would also damage them as the dirt would become embedded in the formation.
They advise you not to take this tour if you are claustrophobic. Discuss your concerns with your guide, who will help you decide if you should do it or take the Adventure Tour instead. In my experience, if you stay close to your guide, and keep your flashlight lit (though make sure you don’t shine it in someone’s face), you should be alright. But if you don’t mind crowds, the Adventure Tour can be an alternative, since you’ll only go to well-lit, large rooms.
Inside, the cave is always a comfortable 72 degrees, though it feels warmer with the humidity. Though this means you don’t need to worry about the clothes you wear, it is important to pay attention to your footwear. Wear comfortable, closed shoes, preferable sneakers, since the ground is not always level and it might be muddy in several places.
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