More than just Mexico City’s central post office, this early-20th-century palace is an Italianate confection designed by the Palacio de Bellas Artes’ original architect, Adamo Boari. The beige stone facade features baroque columns and carved filigree around the windows; inside, the bronze railings on the monumental staircase were cast in Florence. Philatelists can ogle the first stamp ever issued in Mexico in the 1st-floor postal museum.