On our way home from Austin, we saw all these billboards advertising "Inner Space Caverns" so we decided to stop for lunch and check it out. They stumbled on these caverns while drilling the I-35 highway, and they were pretty cool! The girls were troopers, walking almost a full mile through the caverns and back during the tour.
In the caverns they found bones from the wooly mammoth, saber tooth tiger, a type of horse and camel that are extinct, and others.