This was my first time in Rome, end of May 2016. I know, it was too late.
Firs, avoid the museums. Too much time in the lines, so it will take a lot of time. If your absolute priority is the Vatican, than try going there first thing in the morning, but don’t expect to have much time after that, especially if you want to visit the Sistine Chapel. It is really amazing and awe inspiring experience, but I decided to enjoy it the next time.
So, 1 DAY IN ROME… You can start with the Colosseum or St Peters Basilica, everything else is in the middle. Apparently there are people trying this, and it is pretty doable,
Some people actually try to “do” Rome in a day. Crazy as that sounds, if all you have is a day, it’s one of the most exciting days Europe has to offer. Start at 8:30 at the Colosseum. Then explore the Forum, hike over Capitol Hill, and cap your “Caesar Shuffle” with a visit to the Pantheon. After a quick lunch, taxi to the Vatican Museum (the lines usually die down mid-afternoon). See the Vatican Museum and take a short-cut from the Sistine Chapel directly into St. Peter’s Basilica. Taxi back to Campo de’ Fiori for dinner then walk to Piazza Navona for dessert .”
In that moment, it was my favorite place in the world!