The Lusitanian Basin is a rift basin located on both the mainland and continental shelf off the west-central coast of Portugal. It covers an area measuring 20,000 square kilometres (7,700 sq mi) and extends north-south from Porto to Lisbon. The basin varies between approximately 130 kilometres (81 mi) and 340 kilometres (210 mi) in width and belongs to a family of periatlantic basins such as the Jeanne d'Arc Basin. To the east of the Lusitanian Basin lies the Central Plateau of the Iberian Peninsula. A marginal horst system lies to the west. The and Algarve Basins connect to the southern end of the Lusitanian Basin. In the north, it connects to the Porto and via an undersea ridge.