Angels and Demons tour in Rome
Dan Brown’s book about the Illuminati has a tour (not affiliated with Dan Brown, as far as I can tell) that takes you to the places from the book.
When the movie was filming, Tom Hanks and the other key players actually took the tour to help them prepare for their roles.
The tour website: http://www.angelsanddemons.it/
Sites include St. Maria del Popolo Church, St. Peter’s Square, Piazza Navona, and others