On top of being shock-resistant, the bunker was designed to be radiation-proof. It was intended to accommodate 535 officials for 30 days, the estimated time it would take for radiation to fall to an acceptable level and enable the Diefenbunker's inhabitants to return to the surface.

According to Canadian Cold War expert Dave Peters, the complex was contained within a concrete box measuring 154 feet on each side, with approximately 100,000 square feet of space distributed across four levels ranging from the highest floor (400 Level) running down to the lowest level (100 Level), which was used for mechanical systems, storage areas, maintenance facilities and military sleeping quarters.

Inside the Diefenbunker: the secret Cold War bunker built to protect Canada’s elite