According to TCM's Eddie Muller, the reason the sets might look familiar is that they are the same sets James Whale used in Frankenstein (1931).
Even though the film takes place in Austria, mostly in Vienna, most of the crew were native Americans. Paul Lukas was the only one who was actually a native to Germanic Europe, having been born in the Austrian-Hungarian Empire.
Frank Morgan and Charley Grapewin, of course, co-starred some years later in The Wizard of Oz (1939).
One of 3 films in which Frank Morgan and Walter Pidgeon both appeared, the others being Saratoga (1937) and White Cargo (1942).