when i was last in germany, we went to Koln by train, and, as we approached, everyone said, german and americans alike, "look at the dom!" (in english, just like that). I translated it to: "look at the DOME" ie, sports arena with a dome roof... not DOM, german for Cathedral! So, i said, screw the dome, look at the church!
anyway.. koln is an impressive city.. i recomend visiting it if you have the means/time/etc. Germany in general is a wonderful trip.. Also, tour the rhine and mosel rivers.. cant walk 10 feet w/out tripping over some castle or other!