Aug 2, 2011: Images of the world's 10 largest excavations and natural chasms

Turkmenistan's central Derweze area is known for its rich natural gas deposits, and the Burning Gates is a natural phenomena that, while it looks like a volcanic crater, is actually a pit of burning methane and other natural gases. The pit was formed during a drilling operation in 1971 when geologists tapped in to a cavern filled with natural gas. The prevent it from escaping, scientists decided to burn it off. Forty years later, the pit is still alight. Locals have dubbed the 70 metre diameter hole 'The door to hell'.