Behind the red apartment buildings and yellow building all the way at the end of the street. But I think I figured out why that is happening. It could be that those buildings are too close to the barrier and is causing some kind of problem. When bumping into a building, I can't go through. However behind those buildings I can just phase through in the back and then fall straight off. I don't know if I wasn't suppose to do this, but I kept bumping into the walls. First time nothing happened, but second or third time I was able to clip into the buildings. The same thing can be said about the barrier, rammed it enough time and I can pass through.