We have this place back in my home town, it is a nature sanctuary called the Audubon.
Its free and like a 5min drive away.
First you gotta walk down these steps through the woods until the main path forks. We usually go to the place called The Rockery and to get there you have to cross these wood walkways that go directly over the marsh. If you bring sunflower seeds the birds will land and eat off your hands. Once you get across these walkways you follow another path trough the woods and you arrive at this large man made cave that has stone stairs going up to the top from like 5 different directions. On the top of the cave is an opening with a tree in the middle and mad rocks to sit and chill on, we usually spark here. It also over looks a large pond.
After the first blunt we usually walk around the pond via the walkways again and just chill. Its made peaceful and quiet, great place to relax.
But there is so much more than just The Rockery, there are a lot of paths that twist around the entire forest. One go goes to a wooden tower that overlooks a huge marsh, smoking at the top is sick. The other paths just twist around the forest, mainly just so sights.
Its one of the best places I have smoked, we even make trips to go back home and smoke there.
Well thats my expirience lol, stoned and thought i had to share
EDIT:
Almost forgot about this lol I made this stop-motion video with me and my buddies a couple of years ago, in the end you can see some of The Rockery, check it!
http://www.youtube.com/watch?v=GVEV4qigYAk
JJD