Australia's famed Great Barrier Reef stretches 1,600 miles---so big, it can be seen from space. It is the largest structure on Earth built by any living creatures, dwarfing the biggest human constructs. It is also one of the most threatened, facing the risk of collision with ships that navigate the reef, and other dangers such as bleaching, a condition caused by warming ocean temperatures.
Off the coast of Mindoro Island in the Philippines lies Apo Reef, thought to be the second-largest coral reef system in the world, after the Great Barrier Reef. As with many coral reefs, it has been the subject of drastic environmental action to protect its fragile ecosystem, including a total ban on fishing that was enacted by the Philippine government in 2007.
An inlet of the Indian Ocean, the Red Sea lies between Egypt and the Arabian Peninsula. Its shallow shelves create a series of coral reefs that stretch for 1,240 miles along its coast.
Near Australia and the French colony that gives it its name, the New Caledonia Barrier Reef stretches for 930 miles along the Pacific Ocean floor. Because the area is less populated than Australia's coastal regions, it faces less environmental danger than the Great Barrier Reef.
The Indian Ocean, lying between India, Africa and Australia, is home to numerous coral reefs. Near India, the island nation of Maldives is entirely made of coral atolls, islands that formed out of coral reefs. The Maldives reef system is almost 600 miles long.
The Mesoamerican Barrier Reef System stretches along the eastern coast of Central America. From its northern point off the Yucatan Peninsula in Mexico to the southern coast of Honduras, the reef reaches a total of 560 miles.
The Florida Keys Reef Tract is the largest coral reef in U.S. waters. Stretching from Miami to Key West, the reef is 221 miles long.
Off the coast of Africa is Madagascar, an island nation. Its territorial waters include the 200-mile Toliara reef, sometimes called the Tulear reef system.
The Belize Barrier Reef is 186 miles long. It runs parallel to the coast of Belize, a small nation just south of Mexico. Like many coral reefs, it is a popular spot for scuba diving.
Not far from the Belize Barrier Reef, the Andros Island barrier reef stretches for over 140 miles in the Bahamas. Despite its proximity to the United States and Bahamas vacation resorts, it is one of the least visited areas in the Bahamas.
