Around two million people annually visit Spanish architect Antoni Gaudí's unfinished "gesamkunstwerk," La Sagrada Família--a massive church in Barcelona, which was begun in 1883. Since many of Gaudí's plans for the structure were destroyed during the Spanish Civil War, teams of architects have been continually tinkering with the elusive structure since his death in 1926. Because Gaudí seemingly didn't use regular or repeating forms--relying instead on color, light and organic sculptural motifs--architects working on the completion of La Sagrada Família have faced a...