Largest marine animal structure

The largest marine structure ever built by living creatures is the 2,300-km-long (1,430-mile) Great Barrier Reef, off Queensland, Australia, covering an area of 207,000 square kilometres (80,000 square miles). It consists of countless billions of dead and living stony corals (order Madreporaria or Scleractinia). The structure comprises a series of some 3,000 smaller reefs and 900 islands.

Over 350 species of coral are currently found there, and its accretion is estimated to have taken 600 million years.