Barcelona, the capital of the Spanish province of Catalonia, was an epicenter of 20thcentury architectural vanguardism. The city’s geographic position on the northeast face of the Iberian Peninsula—ostensibly with its back to the Castilian capital of Madrid and its face toward the Mediterranean countries of Europe and North Africa—has sustained its cosmopolitan dimensions throughout its history. From the century’s onset and the separatist-regionalist concepts associated with Catalan modernisme, Barcelona’s architectural primacy has endured two dictatorships, the suppression of its people’s native language, and the dramatic social upheavals associated with industrial expansion and rapid population growth. From the mid-19th century, Barcelona’s municipal authorities sought to cope with the newly industrialized city’s adolescence. The socialist Ildefonso Cerdà i Sunyer (1815–76) created a Haussmannian solution for unifying Barcelona’s Old City with the independent villages of the peripher...