The gothic Basilica was Antoni Gaudí’s last masterpiece, but when he died in 1926 only a quarter of the project had been constructed. In honor of Gaudí’s relationship with his incomplete magnum opus, the artist’s body was buried in the church, placed symbolically in the Basilica’s crypt. With further building interrupted in the 1930s by both the Spanish Civil War and a destructive fire, the church remains unfinished, missing 10 of the originally projected spires. This virtual tour is a chance to see inside its soaring walls. —E.C.