23 miles from Austin, a collapsed underground river made one of Texas’s wildest swimming holes

Hamilton Pool’s collapse made something worth the drive

About 23 miles west of Austin, a jade-green pool sits inside a grotto that formed when the ceiling of an underground river gave way thousands of years ago.

A 50-foot waterfall spills over limestone into the water below. Stalactites hang from the overhang above, and maidenhair ferns cling to the rock face.

This is Hamilton Pool Preserve, and it exists because geology did something dramatic here that it almost never does anywhere else.

The dome fell and left this behind

Long before anyone named it, the Edwards Plateau sat over a network of underground rivers carved through limestone by slow-moving groundwater.

Over thousands of years, that water dissolved enough rock that a section of ceiling collapsed, leaving behind the grotto and pool you walk into today.

Massive limestone slabs from that collapse still rest at the water’s edge. Before the 1800s, the Tonkawa and Lipan Apache lived in this part of Texas.

Morgan C. Hamilton owned the land in the 1860s, and his brother Andrew Jackson Hamilton, who served as governor of Texas from 1865 to 1866, visited the grotto.

The Reimers family, German immigrants, bought the property in the 1880s to raise sheep and cattle. According to local legend, their eight-year-old son stumbled across the collapsed grotto.

The waterfall runs all year, even through dry spells

Hamilton Creek feeds the pool from about three-quarters of a mile upstream, and the waterfall it creates never completely stops. During droughts it slows to a trickle, but the water keeps moving.

The pool level stays surprisingly steady even when the surrounding Hill Country dries out. What changes is whether you can swim in it.

The water hits as cold as 50 degrees and gets no chemical treatment, so county staff monitors bacteria levels and water quality before each visit.

A recent rainstorm or unstable rock can close swimming with little warning.

Hundreds of plants pack into this canyon

The preserve holds 486 plant species across 100 families, and the canyon concentrates most of the rarest ones. The chatterbox orchid, canyon mock-orange, and leather flower all grow here.

Red bay trees line parts of the creek, and this grove represents the westernmost colony of a species that normally stays in the eastern United States.

Above the canyon, juniper and oak savannah cover the uplands with native grasses and wildflowers.

The shift between those two zones, from dry upland to cool, shaded canyon floor, creates two completely different ecosystems within a few hundred yards of each other.

Only one bird on earth nests here in the spring

The golden-cheeked warbler breeds nowhere else on the planet outside Central Texas.

Each spring it returns from Mexico and Central America to the Hill Country, where it depends on mature Ashe juniper trees for nesting material, weaving strips of bark together with spider webs to build its nest.

Hamilton Pool sits inside the Balcones Canyonlands Preserve, a connected network protecting more than 31,000 acres of endangered species habitat.

The county created the BCP in 1996 to protect eight species, including the warbler and six rare invertebrates found only in area caves.

Foxes, bobcats and cliff swallows share the canyon with you

White-tailed deer browse the uplands, and bobcats and foxes move through the preserve mostly at dawn and dusk. Porcupines, skunks, and opossums round out the mammal list.

Canyon wrens and cliff swallows nest along the rocky outcroppings near the grotto, and the pool supports sunfish and carp.

The preserve sits along the Texas Hill Country Birding Trail, and a bird list is available at the entrance booth.

One more thing worth knowing: water moccasins live here, so pay attention to where you step near the water’s edge.

The trail drops 80 feet to the grotto floor

The hike from the parking lot down to the pool runs about a quarter mile and takes 15 to 20 minutes. A series of steep, uneven stone steps drops roughly 80 feet into the canyon.

Wear real shoes. This trail is not wheelchair accessible, and sandals will make the descent harder than it needs to be. At the bottom, the trail forks.

Right takes you to the pool and grotto. Left leads toward the Pedernales River.

The section of trail that runs directly under the overhanging cliff is closed right now because of falling rock risk.

Follow the creek three-quarters of a mile to the river

The left fork at the canyon bottom follows Hamilton Creek downstream to the Pedernales River, about three-quarters of a mile from the pool.

Bald cypress trees line the creek banks and turn yellow and orange in fall, when the canyon walls keep the trail noticeably cooler than the open land above.

The trail ends at a wide, rocky beach where the creek meets the river. When swimming is closed at the pool, the Pedernales River stays open for swimming.

The full round trip from the parking lot to the river and back runs about a mile and a half.

Travis County bought this land and worked to bring it back

By the 1960s, Hamilton Pool had become a popular swimming hole with almost no oversight. Decades of heavy use and livestock grazing wore down the vegetation and damaged the ecosystem.

A 1980 Texas Parks and Wildlife assessment called it the most significant natural area in rural Travis County. Travis County bought 232 acres from the Reimers family in 1985 and launched a restoration program.

Since then, the county has run prescribed burns, restored native prairie, and conducted ongoing endangered species surveys. The fern-covered cliffs and rolling meadows along the trails are showing steady recovery.

You need a reservation, and the slots go fast

The parking lot holds 75 vehicles, and that limit is firm. Reservations are required every day and must be made online before you arrive.

Two time slots run each day: morning from 9 a.m. to 12:30 p.m. and afternoon from 2 p.m. to 5:30 p.m. Summer and weekend slots fill weeks out.

No pets are allowed inside the preserve, not in the car, not on a leash. There are no concessions inside and no drinking water on site, so bring your own.

The preserve is open every day of the year, including holidays.

Bring cash because the gate does not take cards

The online reservation costs $12 per vehicle and covers up to eight people. At the gate, you pay the entrance fee in cash only.

Adults between 13 and 61 pay $8. Seniors 62 and older pay $3.

Children 12 and under get in free. Credit and debit cards are not accepted on site, and all fees are nonrefundable regardless of whether swimming is allowed that day.

If you plan to stop at nearby Milton Reimers Ranch Park on the same trip, ask about the discount for visiting both parks in one day.

The grotto pulls people in even when swimming is closed

Some of the preserve’s busiest days have happened when the pool was not open for swimming. The grotto, the waterfall, and the canyon draw people in all year for hiking and photography.

Fall is worth the visit on its own: the bald cypress turns along the creek, the crowds thin out, and reservations open up.

The cooler months from November through March give you the best shot at an available slot without planning weeks ahead.

Two nearby properties, Westcave Outdoor Discovery Center and Milton Reimers Ranch Park, both sit within a short drive and extend the day if you want more time in the canyon.

Visit Hamilton Pool Preserve in Dripping Springs, Texas

To get out to Hamilton Pool, you can look up current swimming conditions and make a reservation through the official Travis County Parks website before you go.

The preserve sits at 24300 Hamilton Pool Road in Dripping Springs, about 45 minutes from downtown Austin. It’s open every day of the year.

Bring drinking water, sunscreen, cash for the entrance fee, and shoes with good grip for the stone steps. Check the swimming status the morning of your visit since conditions can change overnight.

This article was created with AI assistance and human editing.

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