Austin has a wealth of trail-running opportunities. From easy, flat, shaded lakeside trails, to rugged, rocky, and steep hills, you can find it here. Barton Creek Greenbelt is the hub of central Austin trail runners. It is 7.5 miles of varied landscapes, all of which are beautiful, and yet still right near downtown. The Greenbelt includes challenging sites like the Hill of Life, with its steep inclines and crushed limestone paths. Many runners make it a 15-mile round-trip challenge to start from the Barton Springs entrance, summit the Hill of Life, then return.
On the north end of Austin, Walnut Creek and others offer many miles of trails, although like any trail system, just watch out for mountain bikers.
Outside of Austin, the Hill Country has many parks to choose from for trail running. Places like Lost Maples, Reveille Peak Ranch, and others make perfect day trips.