Post date: Aug 19, 2010 9:44:40 PM
As they flee from the German spies in Austria 1917 ("Adventures in the Secret Service"), Indy & the brothers make their escape into a sewer. The dead-end square where they entered it was Ann's Square (Anenské náměstí) in Old Town Prague.
That large bird-cage-looking thing is actually there as well:
Coordinates:
50.085155, 14.414719