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The Great Barrier Reef is a natural wonder which can be found on coastal ocean tiles. Unlike other natural wonders, the Great Barrier Reef covers two hex tiles that are adjacent to each other. This means you effectively get the discovery bonus twice, which can be an incredible boost for the Spanish. Also, each of the tiles can be worked separately, and each provides the stated bonuses, effectively doubling the Wonder's output!
Note that coastal resources like Fish may be found on Great Barrier Reef tiles, giving their resource bonus, but Fishing Boats cannot work the tile.
Historical Info
The Great Barrier Reef is the world's largest reef. A chain of almost 3000 reefs and 1000 islands, it stretches almost 2600 kilometers (1600 miles) along the coast of north-east Australia. Constructed over 500,000 years by billions of coral polyps, the Great Barrier Reef is the largest single structure made by living creatures. The Great Barrier Reef is home to a hugely diverse population of whales, dolphins, porpoises, dugongs, turtles, fish, octopi, and snakes, not to mention over 200 species of birds.