When I was trying to get the IWHBYD skull I fell and I ened up in a garage and when I steped out I was walking on nothing! First I was walking on buildings and I got to the pelican checkpoint (Where if your trying to get the skull you jumpp down on the ramp to see the pelican fly away) there is a small space between the building your trying to jump to and the rail. Fall in the space and keep on walking.You should end up in a sort of garage.