Three Gates Reef was a large tiger coral reef bordering and forming part of the ecosystem of the underwater city of Myth Nantar. It was 30 m (100 ft) tall and several kilometers wide, and encircled three sides of the city, providing three arches (gates) through which access to the city could be gained. Over the years, the reef was carved with scenes depicting battles and myths. By 1369 DR, the reef had grown out of control and covered up much of the southern part of the city.