As many of you know, this building was initially constructed during the Cold War to serve as the command center for the thirteen missile silos protecting Pittsburgh. What you may not know, is that it was built to withstand a nuclear missile strike, and to keep the occupants alive inside until it was safe to leave again.

Possibly the most amazing feet of engineering in this building is the ventilation system, designed to pump fresh, breathable air through the massive space while the outside world is steeped in radiation.

The above photo was taken inside one of the buildings filtration systems (beer can for size). Each of those vertical inserts is similar to what you might put in your window mounted air conditioner, and this thing has hundreds of them.