We used to have one sort of like you're describing. It was a couple miles of trails away, way back in a heavily wooded area in the middle of nowhere. Nobody knows who built it, even the land owner didn't know it existed until we asked for permission to ride it. He was cool about it and gave us permission as long as we wouldn't hold him liable if we did something dumb and hurt ourselves while on his land.
It wasn't anything huge, but it had the doubles, tabletops, berms, and all that, a flat oval track around the perimeter, and it was pretty cool about how far and tucked away it was that even the land owner didn't know about it and riding there didn't bother anybody. Any given day there was always a couple of guys back there riding or just hanging out.
That lasted a few years before some rich prick bought the outlying property our connecting trails ran through, and put up rails across the trails and no trespassing signs up to keep us away. As far as i know the track is still there, and we have permission to ride it from the land owner, there's just no way for us to access it without breaking the law, and i'm certain that this new prick will call the cops if we sneak past his barricades. Not that the cops would be able to find us, catch us, or do anything about it, but I don't like doing illegal sh*t and giving our sport a bad image. It's still SOOO tempting to go on a little night ride sometime and see how the track looks after all this time, and if anybody else is still riding it.
