What is "ballhausplatz"

Ballhausplatz is located in the first district Innere Stadt in central Vienna, a few minutes' walk from the Austrian Parliament Building and on the edge of the grounds of Hofburg Imperial Palace. Until 1754 the square itself did not exist, as an imperial hospital was located there. Ferdinand I, Holy Roman Emperor erected a real tennis house there, the Ballhaus (ball house). Later the building was used for the Imperial Court Construction Office (Hofbauamt). At the end of the 18th century the Ballhaus was ripped down.