Officially, the Odesa Catacombs comprise at least 2,500 kilometers, or just over 1,550 miles, of generally interlinked tunnels running under the city, as well as into outlying areas. Portions of the Catacombs are known to exist at three different depths at least, with the deepest being 60 meters, or almost 197 feet, below sea level, and there are at least 1,000 documented entry points. It is one of the world's largest known underground networks.