This is another photo, probably of Soviet origin, often misidentified as having taken place in Vienna. Actually, during the winter of 1944-1945, the red flag is being displayed by Soviet soldiers on a lamp post standing just in front of the Hungarian parliament, located behind their backs, and not visible in the photo. 

Across the square (where the Revolution of 1956 began, with yours truly getting really hoarse one day), on the left, stands the ornate Royal Supreme Court of Hungary.

Soviet Red Flag Displayed in Budapest, not Vienna

During the winter of 1944-1945, Soviet troops march through Budapest near the Hungarian Museum of Applied Arts visible in the background. This picture is often misidentified as an event taking place in Vienna.

Soviet Troops in Budapest, not Vienna

Russian officers await the Americans at outside the town of Torgau.