A glitch in the controls of the Snivelak car allows you to pass through walls:
First enter the car and collide head on with a wall,
Press and hold X L1 R1 and LAnalog (down), the front of the car points up and raises slightly, then moves into the wall and drops down (if not release X then hold it again)
Next release L1 and you pass through the other side of the wall.

This gives access to a few sections of the museum that usually can't be reached one of these voids is behind the curved wall near the car.