As you walk through the doors thay slam shut forming a wall on this side with no visible means of opening. The only way to go is onwards...
You find yourself in a completely white room, with no obvious markings to suggest its purpose. Light is streaming in through a slit in one wall, through which you can see the desert floor far below, whilst above a blanket of cloud surrounds the top of the pyramid. You can see a trap door in the ceiling, just reachable from the floor.
The only out of here is upwards through the trap door.