The smallish Plaza Manuel Tolsá—at the end of Calle de Tacuba—is an all-but-perfect urban conglomeration that will thrill architecture fans. To the south lies the 18th-century Palacio de Minería (a former engineering college) whose solid, sober mastery of imposing volume is leavened by the wavy effects of the city’s sinking soils; to the north is the former Palacio de Comunicaciones, now Mexico’s National Art Museum. The collection here is a winner—but some of the structure’s soaring neoclassical spaces will leave you agog. At the corner with the Eje Central thoroughfare stands the city’s beloved old post office, noted for its eclectic, Venetian-style facade and coruscating interiors in marble, bronze, and iron (don’t miss the grand staircase). A recently restored equestrian statue of a somewhat dopey-looking King Charles IV of Spain is a marvelous finishing touch.