One of Madrid’s hidden cultural gems, up to now only accessible to private guests or art aficionados willing to endure a near three-year waiting list, the neoclassical Palace of Liria will open its doors to the general public from September  19.

Home to the 19th Duke of Alba, a Grandee – or highest nobility – of Spain and head of one of its oldest and richest aristocratic houses, it boasts paintings by Francisco Goya, Diego Velazquez and Peter Paul Rubens and a unique library with letters penned by Christopher Columbus and a first edition of Don Quixote.

The 18th century building is the third palace the Albas have opened to paying visitors since 2016 in an effort to maintain the heritage of the family, which is restricted from selling many of its heirlooms due to their historic importance for Spain.

The House of Alba dates back to the 1400s and its wealth is estimated to be between 600 million euros and 3.5 billion euros (663 million U.S. dollars – 3.87 billion U.S. dollars).

The Palace of Liria, where France’s last empress and wife of Napoleon III, Maria Eugenia de Montijo, died in exile 1920, will allow groups of 20 visitors to tour its ground and first floors every 30 minutes for a 14-euro (15.50 U.S. dollars) fee.

Duke Carlos Fitz-James Stuart and his family will continue to live on the second floor of the palace, which was extensively rebuilt after suffering heavy damage from bombing in Spain’s 1936-39 Civil War.