Dorne is bordered by the Sea of Dorne to the north, the islands known as the Stepstones to the east, and stretches from the high mountains of the Dornish marches, the Red Mountains, separating Dorne from the remainder of the Seven Kingdoms by land. The two major passes through the Red Mountains that connect Dorne with the rest of the continent are the Stone Way Pass and the Prince's Pass. The Prince's Pass leads to the Reach, while the Stone Way exits the mountains near Summerhall. The southern coast of the continent is bordered by the Summer Sea. Described as tropical in climate by George R. R. Martin, Dorne has the highest temperatures of any kingdom in Westeros, and is arid, with a rocky, mountainous, terrain that includes the only desert on the continent. Its rivers provide some fertile lands and during a long summer there is enough rain and other supplies of water to keep Dorne habitable. Inland water is almost as valuable as gold, and wells are jealously guarded. Notable locations of Dorne are Starfall, the seat of House Dayne, and Yronwood, the seat of House Yronwood, the most powerful of the Martell bannermen. Planky Town is a trade port town at the mouth of the River Greenblood.