Henry L.
Yelp
Based on the number of reviews so far, a.k.a one, this doesn't sound like a well-known area. I didn't know about this place either, but being relatively far away from civilization, this green belt has a lot going for it.
Note that this is the Twin Falls side of Mopac. I came with a group of coworkers for volunteering with Keep Austin Beautiful. Our job is mainly to walk up and down the trails and pick up trash, separating the waste from the recyclables. It had just poured rain the night before, so the weather was excellent with plenty of shade from the trees, but the trails were a bit muddy. Parking is pretty plentiful as well. If you're not sure where the entrance is, go to google maps and search for 'Sculpture Falls Parking'.
This trail is one of the most nature-y greenbelts I've been to in Austin. There are obvious paths, but none of it is paved. Although the trail is relatively narrow, it's pretty good for walking, biking, walking your dogs, and swimming. What, swimming?? Yes! Bring your swim trunks and/or tubes cause the river is flowing and feels great! I didn't exactly jump in since I'm on the job, but I did dip my feet in. A lot of people and their dogs were hanging in the water and it looks super fun. The envy is real.
One downside of being so immersed in nature is that the muddy trails make navigation pretty difficult in several areas. But if you're adventurous enough, you'll get a big dose of rushing waters, large fields of wildflowers, and the wildlife. Bring insect repellent and watch for snakes! Oh by the way, no portable toilets here, so use the restroom before coming or prepare to hold it!
If you have an afternoon to kill, come down to this greenbelt. No matter how much time you have on your hands, you won't be able to get through it all. The main trail has a lot of mini paths branching off of it as well. I'll definitely stop by for a second visit, this time sans large trash bags.