The Royal Library of El Escorial occupies the ground floor of the main building, a single magnificent hall 55 metres long with barrel-vaulted ceilings painted by Pellegrino Tibaldi with allegorical frescoes representing the seven liberal arts. The bookcases were designed by Juan de Herrera, the monastery's architect, in a dark wood inlaid with ivory, and the books are stored spine-inward — an unusual arrangement that was thought to protect the bindings.
The collection includes around 40,000 volumes and 5,000 manuscripts in Arabic, Greek, Latin, Spanish, and Hebrew. The most famous single item is the Codex Aureus of San Millán, an 11th-century illuminated manuscript in gold lettering. The library is included in the general ticket for the monastery complex and should not be missed.