"Pedernales Falls is the park's main attraction and may be viewed from a scenic overlook at the north end of the park. In this area, the elevation of the river drops about 50 feet over a distance of 3000 feet, and the cascading falls are formed by the flow of water over the tilted, stair-step effect of layered limestone."
---Texas Parks & Wildlife Website
Pedernales Falls
My family loves this park. First go take a look at the falls. It's a downhill grade to the viewing area. It's longer on the way back for some reason, especially in the summer. You can continue on down to the banks of the river although there is no swimming or wading, with strict fines.
Head down river a bit and jump from boulder to boulder to explore. Dogs were in tow by several people -- or rather people were in tow behind their dogs - so I assume dogs are allowed to frolic here. 
Once you've had your fill of this area, get back in your car and drive to the river parking. This is the spot where you can actually get wet. It's another hike down a loooong wooden-planked set of stairs. Again, it's much steeper and longer on the way up.
You could easily while away a day at Pedernales Falls State Park if you pack in your own water and food.
Open: 7 days a week year-round, except when wildlife management activities dictate closure of all or part of the park
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