Prado Museum

It opened in 1819 in a building Juan de Villanueva had designed as a natural history cabinet, and today it is one of the world's great art museums. Its strength is the Spanish, Flemish and Italian painting gathered by the monarchy over centuries.

This is where you find Velázquez's Las Meninas, Goya's Third of May and Black Paintings, Bosch's Garden of Earthly Delights, and works by Titian, Rubens and El Greco. Seeing it all in one visit is impossible: better to choose a few rooms and see them properly.