This enormous, cathedral-like building is the main water tank of the Metropolitan Area Outer Underground Discharge Channel facility in Tokyo, which is the world’s largest underground flood diversion facility. Read More >>
Every year millions of tourists flock to London to marvel at its historic buildings, parks and attractions, but if you scratch beneath London's surface, you'll reveal a dark, intimidating web of abandoned stations, military tunnels and historic catacombs.
Armed with high-tech lasers scanners, cave explorers are slowly mapping hidden underground worlds. And now they've found the world's largest cave chamber, equivalent in size to four Great Pyramids carved-out underground.