We took a day-long field trip to Innerspace Caverns in Georgetown, Texas. https://innerspacecavern.com It's located 30 minutes north of Austin off 35. We paid about $20 per person for the Adventure Tour (there is a coupon on their website to print out and bring). They have more intense tours you can take where you need flashlights, kneepads and gear, because you crawl through spaces, etc. We obviously did not do that with a 7 year-old. The Adventure Tour was a very safe tour if you're bringing small children and we did walk about a mile through the cave system, going almost 100 feet underground (actually under 35).
This was a great Earth Science or Geology tour! I did take some pictures, but my phone struggled. You can't use a flash and there were bats - we saw two of them on the tour. They don't want camera flashes to scare the bats, for obvious reasons.
The tour starts off very cold, but warms up to 72 degrees with 98% humidity, so we were freezing at the beginning and sweating at the end.
They did completely turn off all the lights for a moment at the deepest part of the cave, which was really cool!
What was interesting about the cave was part of the cave ceiling was a fossilized ocean reef from when Texas was covered in a shallow ocean.
The Animal Room had paintings on the wall from an artist depicting different prehistoric animals that had fallen through the roof of the cave and their skeletal remains were found inside the cave. White tail deer.
Giant Ground Sloth
Glyptodont - prehistoric armadillo
Prehistoric horses
Sabertooth tiger
Colombian Mammoth
The entrance was an artificial opening blasted into the rock