Natural Bridge Caverns are truly some of the of spectacular caves in North America, and one of the largest in the state of Texas (which is, as we all know, known for big things). There are a number of different tour options, from their most basic Discovery Tour, to more adventurous ones (some involving climbing and rappelling). Whatever you choose, you'll be amazed by the natural beauty here.
Sitting in your car while visiting animals in the zoo was an interesting experience. The animals are tame enough to come next to your car, and you can feed them from the baggie of food that you're given at the entrance. Be aware that any damage to your car is on you—those antelopes don't carry insurance!