Great Blue Hole

A giant marine sinkhole visible from space off the coast of Belize/Natural Wonders

The Great Blue Hole is a giant marine sinkhole off the coast of Belize near the center of Lighthouse Reef atoll. It is roughly 318 meters across and 124 meters deep, making it one of the world's largest natural sinkholes. The hole formed as a limestone cave system during several glacial periods when sea levels were much lower, then flooded as ice melted and oceans rose. Jacques Cousteau declared it one of the top ten scuba diving sites in the world in 1971. Stalactites found at a depth of about 40 meters confirm the cave's terrestrial origins.