The River Walk, The Alamo, Tower of the Americas, The Natural Bridge Caverns and when you want to relax head on out to New Braunfels and stay in a cabin along the Guadalupe River.
The Alamo is definitely on the list. Just looked up the natural bridge caverns. That looks pretty cool also. Would it be possible to do the Alamo and the caverns in the same day or would it be best to split the days?