Barton Creek Greenbelt
In addition to Lake Travis and Lake Austin, Barton Creek Greenbelt is a fun place to swim when the weather is warm in Austin (and there's been enough rain to fill its swimming holes). You can also come here to bike, hike (there are several miles' worth of trails), or just wander around. The Greenbelt is a several-mile, several-hundred-acre stretch that begins at Zilker Park, which is the best playground in the city for littles. There's a train ride that goes around the park—get a popsicle before jumping on. You can also paddle-board or rent kayaks to take out into the lake that crosses the middle of the city. (The baby turtles always keep the kids entertained.) In the center of the park itself is Barton Springs Pool, a three-acre pool that is fed from an underground spring; you pay a small fee to swim. The water in the natural watering hole is kept around 68-70 degrees, which feels just right on a scorching day. The pool is open daily, but closed most of Thursday for a weekly cleaning.