The big imperial palace complex that houses a few of the city top sites: Sisi Museum, imperial apartments, and a silver museum.
The Hofburg is the official residence and workplace of the President of Austria and was formerly the principal imperial palace of the Habsburg dynasty. Located in the center of Vienna, it was built in the 13th century and expanded several times afterwards. It also served as the imperial winter residence, as Schönbrunn Palace was the summer residence. (Wikipedia)
Today the Hofburg palace houses three museums: the Imperial Apartments with the original royal collection of furnishings and decoration, the Sisi Museum that illustrate the true personality of the frequently misunderstood Empress, and the Imperial Silver Collection gives visitors a fascinating insight into the culture of formal dining at the imperial court.