Historic villas dot Hietzing, the 13th District, one of Vienna’s most affluent neighborhoods. Baroque Schönbrunn Palace, the Habsburgs’ summer residence, draws visitors to its opulent interiors, while walkers enjoy the gardens and zoo.  This old, unused sepia postcard is heavily aged and stained (mildew?) on the reverse, but the front is still OK and the card is undeniably authentic.  Grade: 3