The Bibliotheca Alexandrina perpetuates the tradition of the ancient Library of Alexandria, once among the largest libraries in the world. The idea of reviving the old library originated in 1974. It took twenty years to begin construction, and the new library was inaugurated in 2002. It occupies a plot of land close to the site of the original library. The design was selected after a worldwide architectural design competition organized by UNESCO that attracted more than 1400 entries. The Bibliotheca Alexandrina can hold eight million books. The main reading room covers 20,000 square meters (220,000 square feet) on eleven cascading levels under an impressive glass-panelled roof tilted out towards the Mediterranean sea like a sundial. The complex includes a planetarium, four museums (Antiquities, Manuscript, Sadat, and History of Science), and a manuscript restoration laboratory.