I've visited many beautiful cathedrals and such in Europe, including one inside a mountain. I've performed a jazz concert in the cathedral in Ely, England. The sound was awesome.Haha funny. Ever been? My neck hurt for a week after spending few hours there, most beautiful frescos in Rome, besides the Sistine chapel of course.
I'd go on a mission to visit all the cathedrals in Europe if I had the time and money, and carefree.