Deciding what to see in Rome in one day is a real challenge. The city with the largest historic center in the world is difficult to discover even by the Romans themselves but nothing is impossible, you just need to be clear about what you want to see.
The best advice for visiting Rome in one day
Luggage, carrying them around Rome is uncomfortable and dangerous (theft), so choose a luggage storage in the center of Rome or in the point that suits you best, and book it before leaving.
It all starts with what you want to see in Rome specifically
Do you have a museum that you absolutely want to see or a place of interest that you don't want to miss? Start with that. From there, then establish the itinerary.
What to see in Rome in one day: the unmissable places of the Eternal City
Rome I divide it into three areas:
archaeological area: with the Imperial Forums, the Colosseum and the Capidoglio
spiritual area: St. Peter's and the Vatican Museums with the adjoining Castel Sant’Angelo
shopping area: Trevi fountain, Spanish Steps, Via Condotti, Via del Corso and Piazza del Popolo
Is there anything else to see in Rome in one day? Yes!
It all depends on how much you feel like walking and exploring. In this case, I also recommend that you take the metro, so that you can travel to the main places of interest quickly.
The places / monuments / unmissable things of Rome (in my opinion)
Below I will make you a short list of all those places that are not to be missed and that you must see at least once in Rome. These things are mostly taken for granted but it is always good to repeat them and mark them in your itinerary:
The Colosseum and the Imperial Forums. I suggest at least the first time, to also visit the entire internal area, walking among the ruins is something suggestive;
Piazza di Spagna. Elegant, beautiful, colorful, it is one of the places I love most in Rome;
Trevi Fountain in the early morning. When there is only the sound of the water and very few people around, the perfect moment;
Piazza del Popolo and the Pincio. A majestic square with the Pincio terrace which is among the most beautiful in Rome. Above all, on the Pincio there is a splendid park and the equally beautiful Galleria Borghese, a must for art lovers;
San Pietro and the Vatican Museums. Expect to lose half a day or maybe even more just there. The Vatican Museums are large, varied and stupendous, among the most beautiful museums I have ever seen and with them St. Peter's Basilica itself. I chose to book a luggage storage near the Vatican and St. Peter's Basilica
Castel Sant’Angelo, snubbed by many, instead has beautiful interiors;
The panoramic points of Rome, look for them along the way;
Piazza Navona and Campo dei Fiori, two splendid and characteristic squares of Rome, beautiful especially during the various markets and flea markets;
The Pantheon, the interior is evocative and above all free;
The imposing Vittoriano dominates Rome and is part of its skyline, from its terrace there is one of the most evocative views:
The Campidoglio, three panoramic terraces, one of the best places to greet Rome, both from above and from its museum, in fact here are the Capitoline Museums, another important stop in the city.
As you have seen, Rome is varied and these are just some of the key stages. It is difficult to say what to see in Rome in one day with all these beauties scattered around the city, but what is certain is that whatever you choose, it will always be the right choice.