You've probably not experienced anything like Barton Springs, unless you live in a large city and your city has a spring-fed pool very close to the city center. Like I said; unusual.
Barton Springs is one of a kind, and feeds the "unique Austin" feel. It's a rather large pool, so plenty of room for the whole family, if you want. Since it's spring-fed, the temperature stays close to the same temperature all year, which is nice in the summer. Very refreshing!
Great place to take the family to chill and cool down on a hot afternoon. They even have lifeguards and a diving board. The thermal springs are kept at a nice 68F. Just be careful when walking in the pool and around the pool it can get slippery.