Barton Springs Pool karst limestone spring

Barton Springs Pool in Zilker Park is fed by a karst spring that emerges through Edwards Group limestone connected to the Barton Springs segment of the Edwards Aquifer. The spring creates a natural limestone pool and maintains a year-round temperature averaging about 68–70°F (20–21°C). The pool and its limestone features have been used for public swimming since the early 20th century and are a documented geological and recreational feature of Austin.