Stephansdom, Vienna, Austria
The "Wiener Neustädter" altar. The base of the altar has Emperor Frederick III's A.E.I.O.U. inscription on it. Too bad he forgot to tell anyone just what the inscription meant - maybe it's one of those "you just had to be there to get it" things.
Detail of the outside of the cathedral. The cathedral is currently being renovated to keep it from practically melting under the acid rain and pollutants in the air.