Big fan of cathedrals and visited a few great ones over in Germany. I prefer high Gothic cathedrals next to Romanesque. What I love is wandering around the cathedrals trying to find builder's marks carved into the pillers, looking at built in guild symbols etc. I remember the first time I saw the cathedral in Köln, though. One of the most awe inspiring moments of my life. I was coming out of the u-bahn with a group of other Canadians. Suddenly we look up...and up...and up. It really was reaching for the heavens. Probably the most spectacular building I've ever set eyes on.
Köln
Freiburg interior
Aachen/Aix-la-Chapelle interior
And castles:
Neuschwanstein - Was living in Schwangau and Füssen for a little bit and so only a short distance away from the castle. Really beautiful in spring/winter. Though, honestly, I think the mountains are far more spectacular.
Heidelberg