I recently went to Inner Space Caverns, located in Georgetown, TX. This was discovered in 1963 when the highway department was building an overpass for Interstate 35. The cave had a natural entrance approximately 14,000 to 45,000 years ago. Various fossils have been found in the cave, such as a giant sloth and saber-toothed tiger. The cave is estimated to be around 20-25 million years old.
The modern-day entrance was created with dynamite so people can enter the cave. There is also a museum which has a few artifacts. I went on the Adventure tour, which was a one-hour tour and was $20.95.
Ideally, I would have loved to have used a tripod. However, no tripods are allowed, and I used my Nikon 28-300mm f/3.5-5.6G. This lens has vibration reduction. VR or vibration reduction enables you to shoot at slower shutter speeds. Nikon claims that you can usually shoot 3-4 stops slower than normal.
I shot mainly between ISO 1600 to 10,000, and I got useable images at 28mm and as slow as 1/5 of a second shutter speed. I have posted some pictures of the cave along with a few various other photos. Overall I liked exploring the cave, and I got to get some interesting pictures.