A monument to raw, merciless power, the Colosseum (Colosseo) is the most thrilling of Rome's ancient sights. It's not just the amazing completeness of the place, or its size, but the sense of violent history that resonates: it was here that gladiators met in mortal combat and condemned prisoners fought off wild beasts in front of baying, bloodthirsty crowds. Two thousand years later it's Italy's top tourist attraction, pulling in between 16,000 and 19,000 people on an average day.

Along with the Colosseum, the Pantheon is one of Rome's iconic sights. A striking 2000-year-old temple (now a church), it is the city's best-preserved ancient monument and one of the most influential buildings in the Western world. The greying, pock-marked exterior might look its age, but inside it's a different story and it's an exhilarating experience to pass through its towering bronze doors and have your vision directed upwards to the world's largest unreinforced concrete dome.

Today you'll find the tomb of Raphael, alongside those of kings Vittorio Emanuele II and Umberto I.

However, the real fascination of the Pantheon lies in its massive dimensions and extraordinary dome. Considered the Romans' most important architectural achievement, it was the largest dome in the world until the 15th century and is still the largest unreinforced concrete dome ever built. Its harmonious appearance is due to a precisely calibrated symmetry – its diameter is exactly equal to the Pantheon's interior height of 43.3m. Light enters through the oculus, an 8.7m opening in the dome that also served as a symbolic connection between the temple and the gods. Rainwater enters but drains away through 22 almost-invisible holes in the sloping marble floor.

Trevi Fountain
This fountain almost fills an entire piazza, and is Rome's most famous fountain, its iconic status sealed when Anita Ekberg splashed here in La Dolce Vita. The flamboyant baroque ensemble was designed by Nicola Salvi in 1732 and depicts Neptune's chariot being led by Tritons with sea horses – one wild, one docile – representing the moods of the sea. The water comes from the aqua virgo, a 1st-century-BC underground aqueduct, and the name Trevi refers to the tre vie (three roads) that converge at the fountain. It's traditional to throw a coin into the fountain to ensure your return to the Eternal City. It's usually very busy around the fountain during the day, so it's worth trying to visit later in the evening when you can appreciate its foaming majesty without the hordes.

St Peter’s Basilica
In Vatican City, a city of astounding churches, St Peter’s Basilica outdazzles them all. Awe-inspiringly huge, rich and spectacular, it’s a monument to centuries of artistic genius. On a busy day, around 20,000 visitors pass through here. If you want to be one of them, remember to dress appropriately – no shorts, miniskirts or bare shoulders. If you want to hire an audioguide (€5), they’re available at a desk in the cloakroom to the right of the entrance. Free English-language guided tours of the basilica are run from the Vatican tourist office, the Centro Servizi Pellegrini e Turisti, at 9.45am on Tuesday and Thursday and at 2.15pm every afternoon between Monday and Friday.

Vatican Museums
Visiting the Vatican Museums is an unforgettable experience that requires strength, stamina and patience. You’ll need to be on top of your game to endure the inevitable queues – if not for a ticket then for the security checks – and enjoy what is undoubtedly one of the world’s great museum complexes.

Founded by Pope Julius II in the early 16th century and enlarged by successive pontiffs, the museums are housed in what is known collectively as the Palazzo Apostolico Vaticano. This massive 5.5-hectare complex consists of two palaces – the Vatican palace nearest St Peter’s and the Belvedere Palace – joined by two long galleries. On the inside are three courtyards: the Cortile della Pigna, the Cortile della Biblioteca, and, to the south, the Cortile del Belvedere.

You’ll never manage to explore the whole complex in one go – you’d need several hours just for the highlights – so it pays to be selective. There are several suggested itineraries, or you can go it alone and make up your own route.

Each gallery contains priceless treasures, but for a whistlestop tour get to the Pinacoteca, the Museo Pio-Clementino, Galleria delle Carte Geografiche, Stanze di Raffaello (Raphael Rooms) and the Sistine Chapel. On the whole exhibits are not well labelled so you might find it useful to hire an audioguide (€7) or buy the Guide to the Vatican Museums and City (€10). There are also authorised guided tours (adult/concession €30/25), bookable on the Vatican’s online ticket office.

Campo de ‘Fiori
Noisy, colourful 'Il Campo' is a major focus of Roman life: by day it hosts a much-loved market, while at night it morphs into a raucous open-air pub. Towering over the square is the Obi-Wan-like form of Giordano Bruno, a monk who was burned at the stake for heresy in 1600.

Roman Forum
Today an impressive, if rather confusing, sprawl of ruins, the Roman Forum was once a gleaming complex of marble-clad temples, proud basilicas and vibrant public spaces: the gleaming heart of an ancient city.
Originally an Etruscan burial ground, it was first developed in the 7th century BC and expanded over subsequent centuries. Its importance declined after the 4th century until eventually it was used as pasture land. In the Middle Ages it was known as the Campo Vaccino (literally 'Cow Field') and extensively plundered for its stone and marble. The area was systematically excavated in the 18th and 19th centuries, and excavations continue to this day.

Chiesa del Domine Quo Vadis
This pint-sized church marks the spot where St Peter, fleeing Rome, met a vision of Jesus going the other way. When Peter asked: ‘Domine, quo vadis?’ (‘Lord, where are you going?’), Jesus replied, ‘Venio Roman iterum crucifigi’ (‘I am coming to Rome to be crucified again’). Reluctantly deciding to join him, Peter tramped back into town where he was arrested and executed. In the aisle are copies of Chris