When we were younger, we went camping every weekend, no matter what. We both lived with our parents and had to get away somehow. lol. We've done it in the woods, in the tent, friends' tents, picnic areas, by the river, a rest bench on a walking trail, basically anywhere we could!
The funnest spot though? There was an old abandoned railroad track with a solid concrete bridge (not a high bridge, but street level) with grass growing over the bridge from not being used. There was a stream under the bridge. There was one little clearing and we had sex there a lot. It was so fun and such a secret, secluded place. One time though, we saw a badger a few feet away, and we got up ran like hell; that scared the crap out of us!