The River Place Nature Trail is one of the newest, most scenic, and best maintained trails in Austin. The trail follows Panther Hollow Creek in a small canyon beneath the River Place development. In a 6 mile round trip, the trail gains (and loses) about 500 feet in elevation. All that elevation is gained or lost on natural surface stairways built into the hills. All along the trail, you'll get quiet glimpses of typical Balcones Canyonland vistas, although you'll always see some kind of building or structure.
The main trail is 3 miles out, 3 miles back. A 0.5 mile side trail connects the main nature trail to a trailhead at River Place Boulebard. This hiking trail is tough - you can take a shortcut and hike or run the main nature trail (3 miles), go down the sidewalk of River Place Boulevard to the Uplands Nature Trail trailhead (1 mile), and then take the nature trail back to Woodlands Park.
There aren't any maps of the trail online, but there are very nice maps at all trailheads and at the one main junction for the trail.
One confusing thing is that the trail distances are not correctly signed in the Woodlands Park to River Place direction. You'll notice that the trail distances are all short 0.5 miles. Coming back from the River Place Boulevard trailhead, you'll see the correct distances.
To find the trailhead, park at Woodlands Park and cross Big View Drive to the "Boardwalk" around the pond with a fountain. Walk around the boardwalk to the trail that goes up the hill just past the small fishing shelter on the boardwalk.
This trail is suitable for hiking, trail running, and on-leash dogs. No mountain biking is allowed, and it would be really tough to do even if it was allowed!
Woodlands Park has nice bathrooms with flush toilets and sinks with running water. There is also a small parking lot.