Visiting Rome in just one day is an impossibility. Harsh much, you say? Well, it's the truth!
Even locals hardly know or have visited all the monuments and museums in the city - the burden of living in a place that has been the cradle to several major cultural movements and a civilization that still has an impact on our everyday lives today!
With this out of the way, let's try to be honest: Rome is best visited with at least one week at your disposal. But maybe you're here for another occasion, like a wedding, or your cruise doesn't leave until tomorrow.
Whatever the reason, just be aware of the fact that tough choices will have to be made: for instance, if you get to visit the Colosseum, there's no way you can also do the Vatican Museums in the same day. Unless you do both running (hence not seeing much of either site), or decide to only see the former from the outside, or is OK with you to end your day exhausted and possibly with the rest of your family completely burn out.
This itinerary will consider the Vatican Museums and the combo Colosseum/Forums/Palatine Hill as the major attractions in Rome, for the sake of this mini-guide. Others may disagree and argue that we could have included different destinations but as we mentioned... Tough choices.
Colosseum/Roman Forum/Palatine Hill
If you bought tickets beforehand, you're all set - go in the archaeological site from whatever entrance you prefer. Keep in mind that security checks are in effect, so bulky baggage can't go in. Should you need to buy the tickets, do consider that the entrance on the side of the Palatine Hill (read all about it in our Colosseum tips post) has shorter queues.
You can reach the Forum, and specifically the entrance on via di San Gregorio, by commencing your walk at the Circo Massimo metro station. If you get off the subway at that stop, you get the chance to walk by the Circus Maximus, and admire the majestic stadium. From there, simply walk in a straight line until viale Aventino becomes via di San Gregorio - you need to cross twice at the traffic lights, and you're all done. Reach the entrance of the attraction and begin your tour inside from there.
Another nice stroll taking you to the Colosseum includes getting off the subway on the A line at San Giovanni - you'll be outside the Roman walls by a huge department store called COIN. From there, pass the arches inside the walls, keep on the left and admire the huge Basilica di San Giovanni in Laterano - this was the Papal see before Saint Peter's.
Past the church, you'll have the entrance of the Scala Sancta on your right - crossing the street. But keep walking and cross the square until you find, roughly in front of you and to your right, a small alley called via di San Giovanni in Laterano - the Colosseum is at the bottom of it. Halfway through, you have the Basilica di San Clemente on your right, that of the many layers built one on top of the other. The via di San Giovanni in Laterano will end on the side
Looking for a guide? We recommend against picking one right outside the entrance. Do your research beforehand and choose wisely: some of the guides buy the tickets for you, so make sure you don't end up with doubles!
As mentioned, if you realize you're too tired to complete the tour of the Roman Forum, walk on via dei Fori Imperiali where you can take a good look at them, or follow our itinerary that offers you a breathtaking view of the whole area, up to the Capitoline Hill.
You can complete your day, after lunch and as many breaks as you want, by visiting the Capitoline Museums on top of the Capitoline Hill, the Trajan Markets for even more Roman Forum goodness, or the Altare della Patria, the monument built at the end of WWI to celebrate the war ending and the King at that time, Victor Emmanuel II.
St. Peter's Basilica/Vatican Museums/Castel Sant'Angelo
The church opens at 7am - you might want to consider getting there as soon as possible in the morning, so as to have minimal queueing when due for the security checks. Depending on your level of energy, also think hard about whether you feel like climbing to the dome for a spectacular view of the whole city. A must do, in our opinion, but skip it if you have a child (or two!) to carry along, as the elevator only takes you up to a certain level... Then you'll be on your own.
Remember that with a few notable exceptions (Basilica di San Clemente if you want to see the underground levels, the Bocca della Verità at Santa Maria in Cosmedin) all churches have a free entrance in Rome. So be suspicious of whoever asks you for money to visit them!
The Vatican Museums are really easy to find once out of the church: you muy want to follow all tourists passing the colonnade on your left (granted you have your back to the church), through the door in the defensive walls at Porta Sant'Angelica and following the road with the same name until you reach piazza Risorgimento. From there, keep on the left and keep coasting the Vatican walls until you reach the entrance on viale Vaticano.
Again, for the Vatican Museums, same rules apply as with the Colosseum: get in line if you don't have your tickets but do keep in mind that you might want to buy skip-the-line ones, especially if this is your only day in the city. And again, don't go for guides advertising themselves just outside of the museums or the Basilica: book one in advance, should you need one, and choose among various services offered, including tickets being included in the tour or not.
To reach Castel Sant’ Angelo you can either consider walking or taking a bus (no. 23, from via Leone IV, will get you there in no time!). If you want to skip the bus and enjoy the Prati district, you can either go back to piazza Risorgimento, keep on the right of the piazza and get on a via Stefano Porcari. Keep walking in a straight line (the road will change name and turn into a via Giovanni Vitelleschi) until you see a park - that is the former moat of Castel Sant'Angelo, now turned into public gardens.
Should your tour of the Vatican Museums end back at the Basilica, the trek to Castel Sant'Angelo is even more straightforward: simply walk down via della Conciliazione, take a left at the crossing and you can see the castle. It's up to you to decide whether you want to visit it or it's enough to see it from the outside. If you go for the latter, you'll have more time to reach Campo de' Fiori, Piazza Navona or the Pantheon: in this order, you get closer to them by hopping on a bus no. 62 (the terminal is in an alley at the end of via della Conciliazione) or a no. 40 (there's a stop right at the end of via della Conciliazione, on your left).
Either choice is best visited in the early morning, to make the most of smaller queues. Alternatively, you could visit when everyone goes looking for lunch - between 1230 and 2pm.