The Great Barrier Reef is the largest structure made by living organisms, stretching over 1,600 miles along Australia's northern coast. It is composed of tiny coral polyps that have built calcium carbonate skeletons over 500,000 years, creating a vast reef that can be seen from space. The reef experiences warm, sunny weather year-round and has distinct wet and dry seasons that influence the temperatures from 14 to 33 degrees Celsius.