Dominating the center of the half valley was a double bubble: a large squat dome of transparent material with a smaller round dome set on top, a massive shaft of granite, a mesa, in the center, supporting both like a stalagmite tent pole. Inside the upper dome of clear material could be seen scaffolding and rigging similar to that used on oil fields. The large lower dome was squalid, filled with gray machines, pumps, and what looked like some kind of processing plants. On the ground level was a wall of interlocking granite slabs, thick and tall, ringing the floor of the dome, an inner wall of protection.