Hamilton Pool Nature Preserve, Travis County, Texas. One of central Texas' best-kept secrets - a huge azure-blue grotto that makes the perfect summer swimming hole.
The karst topography of the Hill Country region of Texas can result in some pretty interesting geologic features. Many thousands of years ago, an underground river carved through the soft limestone rock, forming a massive dome-shaped underground cavern. Eventually, the cavern collapsed, creating a huge U-shaped grotto. Today, water flows down fifty feet from the overhanging lip of the grotto overhead, into a deep blue pool, before flowing along the cypress tree-lined Hamilton Creek on its way to the Pedernales River.
For many years, Hamilton Pool was on private land - but the area was slowly being trashed and over-run by visitors from nearby Austin. In the 1980's, the area was purchased by the county and turned into a nature preserve, to help control human impact on the area. The pool still draws tens of thousands of people each year, many to swim in the grotto to break the Texas summer heat.
Pictures taken on a nearly-deserted weekday afternoon, March 26, 2008. First a walk through the grotto, then down along the trail beside the creek leading to the Pedernales River.
For more information: Official Website
Also a 35-second video I took from inside the grotto Available on Youtube