One of the things that always makes me wonder just how gullible human beings can be is the plethora of Harry Potter and da Vinci Code tours. As far as I'm aware there isn't yet a Lion, Witch and Wardrobe tour of Oxford (though there is a Middle Earth tour of Birmingham) but I'm sure there soon will be.
If you've read the da Vinci Code, be prepared for a shock when you get to know Rome. I spotted quite a few howlers - I know my Roman baroque churches extremely well and I can tell when Dan Brown hasn't done enough research. But for a real in-depth treatment, try Scott's marvellous article "The Dirt on Rome's Earthy Chapel". It came up on Google when I was doing a bit of research for a piece on Rome's skeletons - and it's the most amazing piece. Worth reading, in fact, even if you have no interest at all in the da Vinci code, for its superb explanation of a very complex and interesting work of art, the Chigi Chapel in Santa Maria del Popolo, Rome.