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

Great Blue Hole is a large underwater sinkhole that sits in the centre of Lighthouse Reef, a small atoll 70kms off the coast of mainland Belize in South America. The hole is 300m in diameter and 124m deep, and was formed in four distinct geological stages. It's a popular spot for tourists and scuba divers.