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.
Wikipedia https://en.wikipedia.org/wiki/Palais_Ferstel
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