View from the top of Saint Stephen's Cathedral (Stephandom, Cathedral of Vienna) in Vienna, Austria. If I am not mistaken, the top of the tower from where this picture was taken is the highest point in Vienna.
While I have visited many churches in my travels, this was one that stuck with me. From the inside, every angle had an impressive view with something to catch your eye. From the outside, it is a striking presence in one of the main squares.