24 Famous places to visit before they disappear

Great Barrier Reef, Australia

Covering an area of 344,400 sq km (133,000 sq mi) in the Coral Sea off the coast of Australia, the Great Barrier Reef is the largest coral reef system in the world. Climate changes, pollution and overfishing are among the main reasons why this breathtaking structure composed of billions organism lost more than half of its corals in just about 27 years and some scientists say it can completely die out in just 40 years.