You can spend a lifetime exploring the Great Barrier Reef and still not see all of this colorful coral realm - it’s nearly the size of Montana. Sprawling off the east coast of Queensland, Australia, the Great Barrier Reef is not a single reef but a group of more than 2,800 distinct entities. It stretches over 1,250 miles (2,000 kilometers) north to south and covers some 135,000 square miles (350,000 square kilometers) in total.