It is the second largest and most visited museum in the Basque Country, after the Bilbao Guggenheim Museum and one of the richest Spanish museums outside Madrid. It houses a valuable and quite comprehensive collection of Basque, Spanish and European art from the Middle Ages to contemporary, including paintings by old masters like El Greco, Cranach, Murillo, Goya, Van Dyck, Ruisdael and Bellotto, together with 19th century and modern: Sorolla, Mary Cassatt, Paul Gauguin, Henri Le Sidaner, James Ensor, Peter Blake, Francis Bacon and Richard Serra.