I'm not sure if this was reported before, but I figured I might as well post this.
So, up above Rob's imports I found this spot, which has no collision
And presto! You're under the map!
Now, instead of just adding collision here, I thought it would be kinda neat to hide some kind of secret in this spot, but that's just me.
EDIT: Hm, maybe I should have gotten rid of chat before I took these pictures...