Balmorhea State Park

Fed by the San Solomon Springs, this pool in the West Texas desert, about an hour from Fort Stockton, is billed as the world's largest spring-fed swimming pool. It covers roughly 0.5 hectares (1.3 acres), the water stays at 22 to 24 °C (72 to 76 °F) year-round and needs no chlorine. The Civilian Conservation Corps began building it in the mid-1930s. A restored wetland provides habitat for endangered fish such as the Comanche Springs pupfish.

Besides swimming, scuba diving is also possible here; in the water you will see fish and turtles, but feeding them is prohibited. Allow a few hours for a day at the pool. The park often reaches capacity on weekends, holidays, school breaks and summer days, so park staff recommend buying day passes online in advance. Pets are not allowed in the pool area. You can stay overnight at the campground with electric hookups or in the historic motor court built by the Civilian Conservation Corps. At night, the dark skies are worth staying up for.