Closeup of the visor from the NE corner. At the back of the concrete cover the the building is about 5 feet lower. The roof of the building itself is 15-18 inches thick with 3 1/2 feet of earth over it. The GCP had 12 inch thick concrete walls, the GPMTCP had 18 inch walls. There were double shutters on the observation slot. A set of wooden shutters on the outside hinged at the bottom and would fold down, glass windows on the inside were hinged at the top and would be hooked to a board on the ceiling to hold them up. The pipes stickiing up are vents and would have had vent caps on them to keep rain out.

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