Within Zilker Park's 358 acres lies one of the crown jewels of Austin - Barton Springs Pool. The pool itself measures three acres in size, and is fed from underground springs with an average temperature of 68-70 degrees, ideal for year-round swimming. Over the years, Barton Springs Pool has drawn people from all walks of life, from legislators who have concocted state laws there to free-spirited, topless sunbathers who turned heads in the 1970s. Robert Redford learned to swim at the pool when he was five years old while visiting family in Austin. Today, Barton Springs still attracts a diverse crowd of people and has seen record setting numbers of visitors nearing 800,000 in recent years.