This is a natural formation that can be seen from outer-space and is the largest single structure formed by living organisms. It approximately covers an area more than 344,400 square kilometers. It was selected as a world heritage site in 1981 and is also one of the seven wonders of the world. What am I talking about?

The Great Barrier Reef is the world's largest coral reef system, visible from space and covering approximately 344,400 square kilometers. It was designated a UNESCO World Heritage Site in 1981 and is recognized as one of the Seven Natural Wonders of the World. The reef is located off the coast of Queensland, Australia, and is the largest single structure created by living organisms.