This collapsed grotto, which is surrounded by shady forests, has been turned into a swimming hole, complete with refreshing waterfall. It's also a short, 20-minute drive from Austin-- perfect for hipsters who want a swimming solution that's a little less mainstream. The grotto has a long history. It was once an underground river, until the dome collapsed due to erosion, forming the canyon-like pool we see today. Before the pool was owned by Morgon C. Hamilton, the area was inhabited by the Tonkawas and Lipan Apaches. Then, Hamilton bought the land in the 1860's, and he and his brother, Texas governor Andrew Jackson Hamilton, would frequently visit the grotto. After that, the land was purchased by the Reimers, a family of German immigrants who planned to use the land to raise cattle. According to legend, their 8-year-old son rediscovered the pool. While such a feature could pose problems for cattle-raising, the Reimers recognized the pool's potential as an attraction for public use.  It wasn't until the 1960's, however, that the pool's popularity really took off. In 1985, the Texas Parks and Wildlife Association bought the pool with the intent to restore the area's natural plant and wild life that had been disrupted by years of cattle ranching. Currently, the ecosystems are recovering nicely. Such an incredible area hasn't gone unnoticed by Hollywood location scouts either. Hamilton Pool has been featured in films like 1990's The Hot Spot, 2010's Predators (oh, hello shirtless Adrian Brody) and 2011's The Tree of Life.  If you want to take a dip in the magical pool, then plan on getting there early, because its popularity hasn't subsided. Since the pool is a protected area, there's a limit to how many people can be allowed in at once, and it fills up FAST, especially on hot Texas summer days. According to the Austin Convention and Visitor's Bureau, 21 million people visited in 2012. It's 100% worth any potential wait, though-- I mean, just imagine how good it'll feel to swim underneath that waterfall! -Roadtrippers Hamilton Pool Preserve is a historic swimming hole which was designated a preserve by the Travis County Commissioner's Court in 1990. Located 3/4 mile upstream from its confluence with the Pedernales River, Hamilton Creek spills out over limestone outcroppings to create a 50 foot waterfall as it plunges into the head of a steep box canyon. The waterfall never completely dries up, but in dry times it does slow to a trickle. However, the pool's water level stays pretty constant, even during periods of drought. The uplands of the preserve are a juniper and oak savannah with a variety of native grasses and wildflowers. Several rare plant species including canyon mock-orange, red bay (western-most colony of this eastern species), and chatter box orchid are known to occur in the canyon areas along Hamilton Creek. A unique natural area surrounds this pool, collapsed grotto and canyon, formed by thousands of years of water erosion. Lush plant communities, a variety of wildlife species and natural shelter attracted the area's first inhabitants. Cultural remains date back over 8,000 years. Prior to the 1800s, Tonkawa and Lipan Apaches lived in the area. In the mid 1860s, Morgan C. Hamilton owned the property now known as Hamilton Pool Preserve. His brother, Andrew Jake Hamilton (the 10th governor of Texas), evidently visited this beautiful grotto while he was governor. In the 1880s, the Reimers, an immigrant family from Germany, bought the property to raise sheep and cattle. Legend has it that their eight-year-old son discovered the collapsed grotto.