Medieval Architecture

Today in class we had a slide show about medieval architecture. I really liked learning about this, even though I basically know nothing about architecture. (I'm a little more up on medieval history, thankfully.)
One of the many things I use history class for is travel tips. Hopefully, I will one day go back to Europe, and when I do, I want to see a lot of these things, like Saint Denis and the Monte Cassino.
The last time I was in Europe, I hung out mostly in southern England, which was awesome. I ended up going to a lot of centers for Christian worship. I went to famous places, like Glastonberry Abbey and St. Paul's Cathedral, but I also found myself going to smaller churches, like St. Michael Paternoster, which is famous for holding the remains of a man the Lord Mayor of London four times. Or St. Anne and St. Agnes, where I got to listen to a Mozart concert. Or St. Edmund, King and Martyr, which is now actually a bookstore specializing in, you guessed it, religious books. I went to other churches and had other adventures, and I won't bore you with details, but I ended up being a church obsessive, though hardly on purpose.
If my professor keeps up the discussion on church architecture, it's only going to become worse. My next trip to Europe, whenever that comes, is just going to have more churches.