Hamilton Pool Preserve, Natural waterfall pool formation in Dripping Springs, United States

Hamilton Pool Preserve is a waterfall formation in the Texas Hill Country, about 23 miles (37 km) west of Austin, where Hamilton Creek drops over an overhanging limestone cliff into a circular natural pool. The grotto formed when the roof of an underground river collapsed, allowing daylight to reach the water and ferns and moss to grow on the damp walls.

Before the 19th century, Tonkawa and Lipan Apache peoples lived in the area. In the mid-1860s, Morgan C. Hamilton owned the property, and his brother Andrew Jackson Hamilton, then Texas governor, evidently visited the grotto. In the 1880s the German immigrant Reimers family bought the land to raise sheep and cattle; legend says their eight-year-old son discovered the collapsed grotto. Travis County purchased 232 acres from the Reimers family in 1985 and began an aggressive restoration plan.

The name honours Morgan C. Hamilton, who owned the land in the mid-1860s; his brother Andrew Jackson Hamilton, Texas governor in 1865–66, evidently visited the grotto. German immigrant settlers named Reimers bought the property in the 1880s to raise sheep and cattle, and their eight-year-old son is said to have found the collapsed grotto. The family then opened it to the public, and since the 1960s it has been a summer swimming spot for Austin residents.

Entry requires an online reservation through the Travis County Hamilton Pool Preserve website, and the pool is open daily for hiking and sight-seeing. The trail beneath the overhang is closed, and swimming has been intermittent since the pool reopened in May 2022 because of high bacteria levels. Water quality is monitored regularly, so check conditions before setting out.

The water remains cool and clear even during dry summer months because it is fed by underground springs. Swimming is not always permitted, as high bacteria levels after rainstorms can temporarily close access to the pool.