Casa Batlló, Barcelona

Casa Batlló's dragon-inspired façade, with its 300,000 trencadís tiles, is 50% costlier per square meter than the typical Barcelona apartment block—yet it yields 4 million annual visitors. Gaudí replaced the conventional straight wall with a 12-meter undulating surface, using no right angles across all six floors. The rooftop's ceramic chimney pots, representing spears in Saint George's dragon, remain a defining Barcelona icon.