Located about 25 miles from downtown off Highway 71, nature lovers will revel in the Balcones Canyonlands Preserve, protected area for the endangered Golden Cheeked Warbler and other birds and wildlife. There are picnic tables, restrooms and hiking trails within the preserve but its most popular attraction is its Hamilton Pool. One of the most stunning sights in Texas, Hamilton Pool is a natural pool that was created when the dome of a massive underground river collapsed thousands of years ago. Designated a nature preserve in 1990 by the Travis County Commission, the oval watering hole is surrounded by limestone outcroppings covered with ferns and hundreds of stalactites. The 50-foot waterfall plunges into the collapsed grotto, and the water flows from the pool down Hamilton Creek and, eventually, into the Pedernales River. The pool and creek are not chemically treated so huge catfish thrive in abundance. There is an entrance fee and reservations are required in the summer.