The Algarve covers 4997 km2, extending just south of the Tagus valley to the southern coast of the Iberian Peninsula, joining Spain. Its highest point is Fóia, , in the mountain range of Monchique. It also includes some islands and islets. The region is also the home of the Ria Formosa Lagoon, a nature reserve of over 170 km2 and a stopping place for hundreds of different species of birds. The length of the south-facing coastline is roughly 155 km. Beyond the westernmost point of Cape St. Vincent it stretches a further 50 km to the north. The coastline is notable for picturesque limestone caves and grottoes, particularly around Lagos, which are accessible by powerboat.