Hamilton Pool Preserve in the Texas Hill Country centers on a jade-green natural pool and waterfall created thousands of years ago when an underground river dome collapsed, forming a limestone grotto with stalactites. The preserve protects rare habitat for species including the endangered golden-cheeked warbler and reflects a long human history, from Tonkawa and Lipan Apache inhabitants to ranching by the Reimers family, who later opened it for recreation. Heavy use and grazing damaged the area, prompting Travis County to buy 232 acres in 1985 and begin restoration. Today, habitat protection, water monitoring, and storm-related closures shape public access.