Barton Springs is a group of four natural springs along Barton Creek in Austin’s Zilker Park, significant for both its geology and ecology. Fed by the Edwards Aquifer, it is the main discharge point for the Barton Springs segment of that karst limestone system, with water moving through fractures and caves in Cretaceous rock. Main Barton Spring, or Parthenia, feeds Barton Springs Pool, while Eliza, Old Mill, and Upper Barton are smaller and can sometimes dry up. The springs are also a rare habitat, including the only known home of the endangered Barton Springs salamander, and they remain important as a natural landmark, swimming area, and protected scientific site.