River deltas are areas where rivers reach a sea or ocean, lake, reservoir, or other larger body of water. The sediment carried by the river forms a triangular landform which juts out into the larger water body. River deltas are frequently the sites of towns and cities because trade routes may rely on the river to move cargo further inland. In addition, sediment carried by the river downstream create what is very often an extremely fertile landscape. There may be farms covering the region. River deltas may contain fishing towns, lighthouses, and ports. In fantasy worlds they may be sites of giant monuments or colossi. There may be mangrove forests in the surrounding area.