Museo Nacional Centro de Arte Reina Sofía
The Museo Nacional Centro de Arte Reina Sofía in Madrid is Spain's premier national museum of 20th-century art, famous worldwide for housing Pablo Picasso's 'Guernica'. Prior to becoming a world-class gallery, the sprawling Sabatini building served for two centuries as the San Carlos General Hospital. Built over mass plague graves, it is renowned for ghost sightings of nuns, phantom patients in hospital gowns, and elevators operating on their own.