The grotto was formed when the dome of an underground river collapsed due to massive erosion thousands of years ago.
The pool is a habitat for the endangered Golden-cheeked Warbler and the Cliff Swallow.
The limestone overhang provides a natural cooling effect, often keeping the grotto significantly cooler than the surrounding Texas hill country.
Water from the pool drains into Hamilton Creek, eventually flowing into the Pedernales River.
The preserve is part of the Balcones Canyonlands Preserve, a multi-agency project to protect habitat for endangered species.
Hamilton Pool Preserve is a natural collapsed grotto formed by the collapse of an underground river thousands of years ago. The site features a 50-foot waterfall that spills from the ceiling of a limestone box canyon into a turquoise pool. The grotto is sheltered by large limestone slabs and contains hanging maidenhair ferns and mosses. It is located within the Balcones Canyonlands Preserve system. Swimming status is determined daily based on water quality testing and bacteria levels. The terrain consists of rugged limestone trails requiring navigation over uneven surfaces. Access is strictly managed through a reservation system requiring advanced booking. The pool remains at a constant temperature year-round due to its subterranean water source.
The sandy beach area looking back toward the waterfall and the limestone grotto overhang.
Reservations are mandatory for all visitors and must be secured well in advance online.
Wear sturdy, closed-toe hiking shoes as the trail down to the pool is steep and rocky.
Bring your own drinking water, as there are no concessions available inside the preserve.
Do not attempt to visit without a pre-paid reservation, as entry is strictly denied to walk-ins. Avoid planning a trip after heavy rain, as the pool is frequently closed for safety or water quality concerns.
Reservations are required year-round; the site is subject to temporary closures for heavy rain or poor water quality.
Pack-in/pack-out policy strictly enforced; no pets allowed; no drones; stay on marked trails to protect sensitive limestone and vegetation.
