Lighting an iconic building designed more than a century ago is a challenge—especially when the project was never completed. Yet the inventive solutions for the nave of Antoni Gaudí's La Sagrada Família Basilica in Barcelona—still under construction 88 years after the architect's death in 1926—offer a close-up view of how contemporary designers are bringing this eccentric masterpiece to fruition. Their efforts are a labor of imaginative extrapolation, as anarchist militiamen destroyed all of Gaudí's original plans and models during the Spanish Civil War in 1936, when little more than the four towers of the Nativity Portal were complete. Using pieces of smashed plaster models, surviving molds, photos, written testimonies, and other documents, successive teams of architects have worked since 1940 to push the project forward. In this process, they have filled in unspecified details as best they could, working with artists and craftsmen, with controversial results but great popular success.