Barton Springs Pool is a recreational outdoor swimming pool in Austin, Texas, that is filled entirely by natural springs connected to the Edwards Aquifer. 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 68 °F and 74 °F year-round. The pool's grassy hills are lined with mature shade trees.