Although badly damaged during WWII, this building stands proudly with all its grandeur. Originally, it was meant to be a stock exchange building, which was moved somewhere else and this "palace" is now used as a fancy event place.
Though tourists can't access the palace, you should definitely consider visiting the Freyung Passage, an elegant shopping arcade which is part of the palace complex.
Official Website http://www.palaisevents.at/en/palais-ferstel/
Address Freyung 2, Vienna, A-1010, Austria
Coordinates 48°12'38.807" N 16°21'55.337" E