... viewed at a museum site; the safe holding the two keys needed to start the Titan II missile launch sequence is visible in this underground Command Capsule. Notice the huge springs in the background which served to dissipate the shock of a nearby Soviet nuclear strike.
... not sure how much 'BOING!' they expected from a 'near-miss' - but the launch officers did have seat-belts on their well padded chairs!
all images- Right click- open in New Window= super colossal size!