I visited the Titan Missle Museum thats about a 1/2 or so SW of Tucson, AZ and was amazed at the machining and design of the place. Very similar to the cartoon above in design (large springs on lower level which the ensapsulated building sat on) but the thing that caught my attention most were the hinges on the primary subsurface door.... that thing had to measure 8 ft square and be two feet thick but moved with just a light push.