Köln Cathedral Inside
If you feel overwhelmed standing outside looking up, you won't find any relief inside.  It is cavernous, and you are nothing but an insignificant speck on the floor- which was a goal of the Church when they built these things.  Of course you still have the large-cathedral trappings once inside- copious amounts of stained glass, candle racks, and the ever-present tombs of Somebody-the-Great.