Introduction to the Great Barrier Reef: The Great Barrier Reef is composed of billions of tiny coral polyps. It is the largest and longest coral reef group in the world and one of the seven natural landscapes in the world. It is located in the southern hemisphere, along the coast of Queensland, extending southward from the mainland town of Port Douglas to Bundaberg, with a length of more than 2,000 kilometers, a maximum width of 161 kilometers, and 2,900 sizes. Coral reef island, the natural landscape is very special.