Enjoy building the Great Pyramid of Giza, the Temple of Artemis at Ephesus, the Hanging Gardens of Babylon, the Mausoleum at Halicarnassus, the Statue of Zeus at Olympia, the Lighthouse of Alexandria, and the Colossus of Rhodes.
A coral reef is an underwater ecosystem characterized by reef-building corals. Reefs are formed of colonies of coral polyps held together by calcium carbonate. Most coral reefs are built from stony corals, whose polyps cluster in groups. source wikipedia