Located close to Austin, there are 30 miles of legal biking trails in the Barton Creek Greenbelt in surrounding Texas Hill Country. This is a wonderful, challenging (but not too tough) mountain bike ride through a varied landscape of jungle-like greenery in the heart of town. You can start at Zilker Park and park there, or park off MoPac and take a shorter mountain bike ride. Enter at Barton Springs Pool or on Loop 360 (near MoPac Boulevard).
Overall, Barton Creek Greenbelt is the 4th most popular mountain bike trail of all 59 mountain biking rides in Texas.