The Stephansdom, or St. Stephen's Cathedral[a] as it is known in English, is the centerpoint of Vienna (even though it may not be some from a purely geometric point of view), and some would argue, the center of Austria and the Austrian identity.
It can be noted that the cathedral is, after 860 years, still under construction. They never finished the north tower after temporarily halting construction in 1511.
The High Altar. Took seven years to get it right.
The "Wiener Neustädter" altar. The base of the altar has Emperor Frederick III's A.E.I.O.U.[b] 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"[c] things.
Outside, the Stephansplatz.