Press L1, L2, R1, R2, L1, L2, R1, R2, Select at the options screen. The following rings will be unlocked: Parking Lot, Castle, Stonehenge, Xtreme, Hades, Garden, Undersea, Rooftop, Space Station, USO, Barnyard, Frontier, and the Box. Note: The Cage ring will not be available with this code.