I'm sure this is an asked and answered question so my apologies but trying to find it in a sea of forum posts is difficult. In any case we have a one day cruise stop in Rome. We will take a pre-reserved train from the cruise port to Rome. We want to see the Vatican museums and sistine chapel and the colosseum. I've read that it's imperative to buy advance tickets to skip the line. Go Italy is a site that came up with tickets. Should I buy them there or just directly at the vatican website etc.? Is there any advantage one way over another? Any advice on how much time to give in between the two? Thanks so much!