Barton creek area is good there is a place called the green belt; although its heavily trafficked, but I have seen and caught a few rat snakes there. McKinney falls is a cool state park you got you typical water snakes there. Walnut creek is a maze of hicking and biking trails that's about 10 miles of trails, it sounds like a lot, but they are all in a small area that snakes through and over laps each other to make it 10 miles, but if you stay on the main trail it snakes through the creek a couple times with good venturing off the trail. Also Georgetown lake is really good with a trail going around the whole lake.
I hope this helps
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