IT'S the sheer claustrophobic density of the place which gets to you. Rome, always the Eternal City, has now become the Infernal City. It feels as if too many people are trying to squeeze into a conurbation which can no longer hold them. The traffic hardly moves, buses seem to burst at the seams, and the outdated and rather tatty Metro makes the London tube at rush hour feel positively airy.

Despite these privations, however, it remains impossible to feel anything other than affection for a city which remains historic and timeless. More than virtually anywhere else in Europe, Rome reeks of culture and history, and even the screaming horns and choking pollution of 21st-century traffic cannot dent its glory.

It is arguably at its most moving at Easter, when pilgrims cram the magnificent churches and St Peter's Square, but Rome's role as the centre of the greatest empire in history and of Christianity means it has the capacity to inspire at any time.

The city's legacy of Roman architecture remains astonishing. Ancient walls, ruins and foundations are everywhere. Even today, the great Roman constructions - the Coliseum, the Pantheon, the Constantine Arch - have a beauty and scale which takes the breath away.

In truth, no one should get too romantic about the Coliseum - it stands right next to one of Rome's busiest highways, is covered in pockmarks and grime and smells more than a bit rank - but it remains a truly impressive building.

The same can also be said of the Pantheon, which is the largest and best preserved monument from Roman antiquity. Once a temple to the Gods, it was dedicated to Christianity on November 1, 609 - the date chosen as the Feast of All Saints. Today, the Pantheon still functions as a church. During my visit, tourists stood respectfully as Mass was celebrated.

Rome is, of course, as famous for its churches and religious history as for its Roman architecture. Great churches include St John Lateran, the Cathedral of Rome (St Peter's, by contrast, is the Cathedral of the Vatican) which the Pope uses in his role as Bishop of the city.

The current huge and sumptuous building dates from the sixteenth century. Opposite is something older and far more venerable - the Santa Scala, or Holy Staircase, which allegedly came from Pilate's house and which Christ is said to have traversed at the time of his trial. The original steps are now covered in walnut, and you can only climb them on your knees.

Other great churches include Santa Maria Degli Angeli, with its famous Meridian line, and Santa Maria Maggiore, famed for its mosaics and said to contain the True Crib in the Confessio under the High Altar. This is a deeply spiritual place, although the piety was somewhat spoiled at 5pm when a staff member pressed a button, winding an electric cover up noisily in front of the sacred relic.

On the other side of the Tiber at the Vatican, Bernini's St Peter's Square is a masterpiece of architecture: you expect it to be massive, but in reality it is even bigger than you ever imagined it would be. St Peter's Basilica, the most sacred shrine of Catholicism, is huge and lavish beyond description. Every fitting, from Michelangelo's dome to his stunning Pieta, and from Bernini's baldacchino to the confessio containing the bones of St Peter, is awesome.

Yet the place is so big and bursting with tour groups and stern-faced guards that it is hard to feel the presence of God here. It is just too anonymous and structurally overwhelming.

Of course, no visit to the Vatican is complete without a trip to the museums, which hold the treasures amassed by popes over hundreds of years. The collections, from Egyptology to Etruscan art, are stunning and extremely well laid out, though the highlight, inevitably, is the visit to the Sistine Chapel, now fully restored. The scale of Michaelangelo's achievement is impossible to describe: you have to see it for yourself.

Rome is a relatively compact city, and you can see most of it in a long weekend. If the noise, fumes and crowding get too much, then a trip out a few stops by metro to EUR, Mussolini's modernist model city with its parkland, artificial lake and expansive buildings, refreshes the senses.

Public transport is efficient and cheap and Rome is full of good, small, inexpensive hotels. They're often family run and welcoming, though you shouldn't expect English to be spoken. Your hosts will smile and jabber away happily in Italian: smile back, be equally warm, and pretend to understand. When in Rome, it really is best to do as the Romans do.