Sometimes tours provide useful insight and understanding. We have visited the Vatican on our own and with a tour, and though we know a lot about the Church and its history, we definitely gained insight and understanding from the tour, especially for the Sistine Chapel and the Vatican treasures. Generally speaking, I think tours of buildings (especially churches) are worthwhile as you learn about the structure and how it was built. Museum tours, on the other hand, often skip over pieces that you may want to linger in front of, though you can always return to the particular painting or sculpture.

As for the Colosseum and the Palatine Hill, you can easily explore on your own. Pick up a history book of Rome and you'll have a grounding before you go.

In Florence, we signed up with a tour to see Michaelangelo's David primarily because the wait is so long. Tours go to the front of the line.

Lucy, Toronto