Several revolutionary and ingenious engineering concepts are implemented into the design to meet these requirements, including the oil bearing system, the Serrurier truss, and the mirror support cell. While the road to the mountain is improved, and water and electricity are installed, construction work begins on the 200-inch dome. Cottages are built for some of the important personnel, while other workers live in barracks that are part of a nearby cattle ranch. The telescope piers are anchored to the bedrock 22 feet below, while the dome supports go about 7 feet into the overlying granite. During the summer, everyone on the mountain helps pour concrete, including several Caltech undergraduates and the observatory cooks.
Work proceeds briskly, and the dome is completed in less than two years.
It is a remarkable coincidence that these dimensions are similar to those of the Pantheon in Rome. The dome weighs approximately 1,000 tons, with a plate steel exterior and aluminum panel interior, separated by four feet to allow for dome venting. Two 125-ton shutters cover the opening seen in the center image and slide open at night to allow light through the slit and into the dome. The top section of the dome rotates on two circular rails. Many people who have ridden on the rotating dome have commented that it feels smoother than most elevator rides.