The most significant and interesting Flemish pieces are those by Hieronymous Bosch, a maverick artist of the 15th century who painted eerie, apocalyptic visions of biblical scenes. The Prado owns several Bosch triptychs.

The Spanish collection boasts an unrivalled collection of works by Velázquez, Goya and El Greco. Velázquez' Las Meninas is a bizarre, mysterious group portrait of the Infanta Doña Maria (daughter of the King and Queen of Spain) and her ladies-in-waiting (meninas - dwarves), with the artist himself outlined in a distant doorway. There are more than 140 paintings by Goya - the Prado basically has a monopoly on the artist's greatest works. They include the once controversial and highly erotic Majas (dressed and undressed) and some of his weird and disturbing Black Paintings, peopled by witches, demons and paranoid nightmares.

The Italian paintings include Raphaels, Titians and Caravaggios. The two most interesting works are Fra Angelico's Annunciation (c 1445) and some stunning panels by Botticelli. Among the Flemish paintings are works by Rubens, van Dyck and Breughel. The French collection includes paintings by Poussin and the German collection works by Durero, Cranach, Grien and Mengs.

There is also a substantial sculpture collection (from Ancient Greece and Rome to 16th-century works), decorative arts, drawings and prints.

In April 2007, the Prado opened its €152m extension, designed by Rafael Moneo, which increased the museum's original size by more than half. The new wing includes the cloisters of the former Los Jerónimos church - the ruins were found nearby, dismantled and then incorporated into the structure of the new building.