Many thanks , I wonder where in Vienna? The Habsburg had 3 chapels around the Hofburg and sometimes it was a drawingroom or bedroom in the palace. I actually mean't where did the Gd Dukes marry in Florence...publicly in a state celebration in the city or a family affair in the Pitti Palace?
According to Alois Jahn's "Das Haus Habsburg" Ferdinand and Maria Anna married in the Hofburg (Leopoldinischer Trakt, Kammer-Kapelle St. Joseph).
Then I had a look at the places where the Granddukes married:
Ferdinand III. and his first wife Maria Luisa of Naples: Augustinerkirche, Wien (19.09.1790)
Ferdinand III. and his second wife Maria Anna of Saxony: Florence (06.05.1821)
Leopold II. and his first wife Maria Anna of Saxony: Florence (16.11.1817)
Leopold II. and his second wife Maria Antonia of Naples: Naples (07.06.1833)
Ferdinand IV. and his first wife Anna Maria of Saxony: Dresden (24.11.1856)
Ferdinand IV. and his second wife Alix of Bourbon-Parma: Schloss Frohsdorf, Wiener Neustadt (11.01.1868)