Barton Creek Greenbelt
It's hard to believe that an epic mountain biking course could be located literally in the middle of Texas' 4th largest city, but the Barton Creek Greenbelt (known simply as "The Greenbelt" to locals) delivers. The main intermediate-level mountain biking trail starts at Zilker Park, just across the river from downtown, and winds its way up the bottom of Barton Creek Canyon for 7.25 miles into West Austin before ascending the "Hill of Life", a 1/3-mile, 300-foot climb up to the rim of the canyon. The terrain is a mix of limestone ledges, rock gardens, gravel, and fast dirt track. The trail is mostly intermediate with some occasional advanced obstacles. Some advanced skill will likely be required to clean the whole course.
Barton Creek Greenbelt has seven official trailheads:
Mile 0: Zilker Park (William Barton and Columbus, next to Barton Springs Pool)
NOTE: the addresses above, if entered verbatim, will take you right to the trailheads in Google Maps
Most of the trail is multi-use, but there are sections in which the mountain biking trail and the hiking trail diverge. Hiking-only sections are blocked by wooden gates and indicated with signage. Riding all the way to the Hill of Life requires crossing the creek six times. Although Barton Creek is usually dry, particularly in summer, these crossings can have as much as 2-3 feet of water in them when the creek is flowing steadily. Barton Creek is prone to flash flooding and can form Class IV rapids during and after heavy rain. If there is water in the creek, do not attempt to cross it unless you can easily discern how deep it is.
Starting at Zilker, the trail consists of some easy rock gardens and gravel/dirt track for about the first mile. Passing the Spyglass Entrance, you pick up larger rock gardens and a very rocky, broken creek drop, all of which will require intermediate level skill to clean. The biking trail crosses the creek through deep gravel at Mile 1.5, then goes through a rooty section and a rock garden up in the trees before dumping you out onto the second creek crossing. The second creek crossing consists of a gravel section followed by a 1-foot ledge, followed immediately by a steep, rooty climb to rejoin the hiking trail.
Continuing down the west side of the creek past Mile 2, you are treated to some limestone ledges, including one about 2 feet tall, a couple of short rock gardens, and lots of fast dirt track. Near Mile 2.5, the trail turns left and crosses "Dry Barton Creek", an arroyo that branches off from the main creek channel. If you keep going straight here, this takes you into a great little slickrock section, and several trails cut through the trees on the other end of the slickrock section to rejoin the main trail. Otherwise, you can cross Dry Barton Creek on the main trail. From here to the third crossing at Mile 3.25 is mostly dirt track with occasional small rock gardens and roots. The third creek crossing, just above Three Falls (AKA "Triple Falls"), is a challenging rock garden. After this, the trail becomes easy dirt track until past the Loop 360 bridge.
Crossing under Loop 360, near Mile 4, the trail makes a technical and rocky ascent up the canyon wall and enters the most challenging section of the course. After passing over some big roots and broken limestone, the trail then drops off a steep limestone outcropping and over a series of ledges. After the limestone ledges comes a series of rock gardens and boulder gardens, some of which have very narrow clearance, followed by a drop down into the creekbed for the fourth crossing. You ride for less than 100 yards on the north side of the creek before crossing again at the fifth crossing. Both fourth and fifth crossings are easy.
After the fifth crossing, the trail becomes easy dirt track until the Mopac bridge. From Mopac, the trail continues along the SW side of the creek for another 1.5 miles, beginning with a fast dirt section, followed by some small ledges and rock gardens, followed by an intermediate creek drop, followed by an advanced creek drop near Mile 6. After this advanced creek drop, the rest of the trail on the SW side of the creek is unrideable, but you can hike a short distance up to the spring or backtrack to cross the creek and continue riding on the NE side.
The trail crosses the creek at the Mopac bridge (sixth crossing) over a limestone shelf, which requires intermediate level skill to negotiate. Once on the NE side, the trail consists mostly of fast dirt and gravel, occasional roots, occasional short ledges, and a couple of relatively easy creek drops. There is one advanced (double black diamond) line at Twin Falls (just past Mile 5), followed by a tricky rock garden. Veer right at Mile 7 to get onto the Hill of Life. The ascent of the Hill of Life requires advanced skill, as the hill consists of very broken limestone talus and large ledges. Intermediate riders should be able to descend it, with some care. Disc brakes and full suspension definitely help.
The Greenbelt can be somewhat heavily traveled. When the weather is nice, particularly on weekends and after work, expect to dodge plenty of hikers and dogs. If there is even the slightest amount of water flowing in the creek, the upper section (particularly around Sculpture Falls and Twin Falls) will become clogged with swimmers.