The Hofburg Palace is located in Vienna, Austria.
Empress Maria Theresa had the opera house transformed into a dance hall for the entertaining of a large group of guests.
Vienna, Austria - Hofburg Palace HD (2013) - YouTube (https://www.youtube.com/watch?v=gIYl9bmijqw)
The Hofburg is the formal imperial palace in Vienna, Austria.
From 1438 to 1583 and from 1612 to 1806, it was the seat of the Habsburg kings and emperors of the Holy Roman Empire.
It was the seat of the Emperor of Austria until 1918.