Billionaire Facebook founder Mark Zuckerberg might be building a 5,000-square-foot refuge beneath his Hawaiian compound, but that doesn't come close in size to the world's biggest bunkers. Built by governments and concerned citizens alike, these spectacular sanctuaries are kitted out with everything you might need to survive a nuclear attack. 

Click or scroll on to explore some of the largest shelters on the planet, from Cold War relics to modern-day prepper communities.