While we were in Austin, my brother and sister in law took us to their favorite hiking destination in the area- Pedernales Falls State Park. The park was beautiful and full of interesting rocks ideal for hiking. We arrived early Friday morning and had the entire park to ourselves; our own little rock playground. We had a blast exploring the huge limestone gorge, which is full of little pools, small rapids, gravel beaches, and boulders.
If you are in Austin and have time to hike, I highly recommend Pedernales Falls. It was an amazing place to explore!