Stephansdom, Vienna, Austria
The "Wiener Neustädter" altar. The base of the altar has Emperor Frederick III's A.E.I.O.U.[a] 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[b] to keep it from practically melting under the acid rain and pollutants in the air.