Colosseum was my favourite too
The Vatican was a nice tour, but it kind of made me angry to think of all the corruption that went into its splendour. Marble pillars as high as 4 story buildings and everything gold encrusted, but ah well.
The Sistine chapel is amazing with the creation of man painting, although when you see it for real, its kinda tiny!
Make sure you snap your pictures quickly cos the security get p'd off
When you get off the plane, don't take a taxi!! their con men who charge about 70 euro to get you into the city, when in fact its about 15 Euro trip, and there's plenty of bus's going there and back.
Mind and show us the pictures