Hornsby Bend is an interesting environmental research and wastewater treatment facility. There are some unimproved roads that you can drive or hike as well as some hiking trails that take you along the Colorado River. Along the ponds you can see many different types of birds, so you may run into some birdwatchers, too. The area where the wastewater treatment facility is is very smelly. Be prepared to gag while you hike.
Be sure to ask for a site map at the entrance to see where the trails run.