Visit a magical city under the sea! Coral reefs look like colorful buildings rising up from the ocean floor. These huge underwater colonies are built by tiny animals called coral polyps. An amazing variety of plants and animals live among coral reefs—in fact, reefs are home to more than one million species of marine life! Jaw-dropping photos, a habitat map, and fascinating information will captivate young readers as they learn about these truly spectacular cities under the sea.