Hofburg Palace at night
The Hofburg is a palace opposite the Vienna Rathaus (city hall) and serves as the official residence of the President of Austria. It has also been the house of other powerful people in Austrian history. Through the years though many sections have been added by notable architects and engineers.
The Hofburg has an outer plaza called the Heldenplatz (heroes' square) which has seen many of history's most important events. One of those would be Adolf Hitler's announcement of the Anschluss (inclusion) of Austria to the German Reich in 1938.
Last night, this is the Treffpunkt (meeting place) museum for those who joined the Lange Nacht der Museen (Long night of the Museums) You'd see more about the event in the following days here.
Taken an hour and a half earlier than above photo...