Two military police guard and secure the blast doors to the Underground Complex in North Bay, Ontario. The MP on the left is holding a Sterling sub-machine gun.

Construction began on the underground complex in 1959. These blast doors were installed in 1962 and weighed an astonishing 19 tonnes.

The complex housed the Semi Automatic Ground Environment (SAGE), the original computer system with a mainframe nearly the size as 12 houses!

Learn more http://www.rcaf-arc.forces.gc.ca/en/22-wing/index.page