When you enter, go straight ahead and to the right you will see a vent near the floor get in it. When you exit this elevator, turn left and go staright ahead into the door with a 'security' sign next to it.You will ride this elevator up to the second floor. When you exit the elevator, turn around and go into the elevator that is directly beside it. At the bottom is a welcome sign, go left here and take the elevator up to the first floor lobby entrance.When you get off, go right and down the escalator.
This walkthrough is based on the Let's Rock (normal) difficulty. So sit down and buckle up, this may take a while! The aliens are already there, so make them appear in the 'Extinct Species' exhibit. Now that the FBI has been taken care of, Duke heads to the museum.