This is the grandiose name for Madrid's imposing Correos (Post Office) building, which was completed at the end of World War I by Antonio Palacios and Joaquín Otamendi. An extravagant wedding cake lookalike that gleams cream-ochre above the Plaza de la Cibeles, it's one of the most emblematic images of 20th-century Madrid. An ambitious blend of Spanish and Viennese Art Nouveau, the building is anything but functional in style, and contrasts strongly with the stark modernity of many buildings lining the nearby Castellana Avenue. Inside, it's just as dramatic, with high ceilings, soaring pillars, marble floors, and a palatial staircase. You won't find a more impressive place to buy stamps for your postcards.