The Diefenbunker is a massive underground nuclear fallout shelter built secretly in the late 1950s to protect the Canadian government during nuclear attack. This four-storey structure spans over 100,000 square feet and sits 75 feet underground, yet was never used for its intended purpose. Today, visitors can explore recreated government rooms, living quarters, the medical centre, and the Bank of Canada vault. Guided tours reveal fascinating stories of Cold War paranoia and life inside the bunker. A National Historic Site named after Prime Minister John Diefenbaker.