At the Suburbs level, go toward the downtown area, drive across the gaps, and stop on the second rooftop. Then, slowly turn toward the ocean and look for a power missle on top of the narrow roof nearby. Back-up your vehicle a bit on the current rooftop, and get a good start toward the other narrow rook with the power missle. After you pick-up the power missle, shoot the vent on top of the building to obtain a black cube that will unlock the Prison Passage level in multi-player mode.