Sandomierz Basin (Polish: Kotlina Sandomierska) is a lowland, located in southeastern Poland, between the Lesser Poland Upland, Lublin Upland and the Western Carpathians. Its name comes from the historical city of Sandomierz, and the basin has a triangular shape with the size of around 15,000 km2 (5,800 sq mi). It is drained by the Vistula River, as well as its eastern tributary, the San (both rivers make its northern border).