Vienna's Uhrenmuseum is a compact clock museum in the Innere Stadt, with a collection ranging from small domestic clocks to elaborate astronomical pieces. It is a good short stop if you have already covered the palace museums and want something more focused.
The highlight is the craftsmanship: painted dials, complicated mechanisms, and clocks made as much to impress as to tell the time. It will not take long to see, but the best pieces reward slow looking.