...or how I learned to stop worrying and start a Blog
... when regular won't do it!
... top image is a size comparison between normal steel bar used in 'reinforced concrete' and the nuclear blast resistant type used in construction of this ICBM 'command capsule'.
... as pointed out before; when thinking about these underground structures it is an easy mistake to imagine them tunneled out like a mining operations. They are usually gigantic holes with the structures built at the bottom and then filled in.