text: Barton Springs Pool is a recreational outdoor swimming pool in Austin, Texas, that is filled entirely with water from nearby natural springs. Located in Zilker Park, the pool exists within the channel of Barton Creek and uses water from Main Barton Spring, the fourth-largest spring in Texas. The pool is a popular venue for year-round swimming, as its temperature hovers between about  and  yearround.
  History
  Long before Barton Springs Pool was built, the springs were considered sacred and were used for purification rituals by the Tonkawa Native American tribe who inhabited the area. Spanish explorers discovered the springs in the 17th century, and around 1730 erected temporary missions at the site (later moving to San Antonio).
  In 1837, before the incorporation of the city of Austin, the area was settled by William ("Uncle Billy") Barton, who named three springs after his daughters: Parthenia, Eliza, and Zenobia.  He and subsequent owners of the property recognized its value as a tourist attraction, and promoted it vigorously, thus leading to the swimming hole's lasting popularity.