Rome screams Vatican, it shouts Colosseum and demands that you throw a penny into the Trevi fountain. It's a theme park for history buffs and that's a lot of pressure for a three-day city break. I wanted somewhere with endless piazzas where I could sit sipping coffee in my Jackie O sunglasses; I wanted to buy vintage Italian leather and eat trattoria food.

I left my sunglasses at home, but found everything else I was looking for in the Trastevere, the Italian equivalent of Paris's Left Bank. Here's the history: Trastevere grew out of the harbour in about 200BC, home to Rome's working class and the Vatican-owned tobacco factories and industries. It's next door to the city's ancient Jewish quarter, the "Ghetto", where you can eat kosher Italian. Much of Trastevere is still owned by the Vatican, and many parts have benefited from the facelift Rome was given for the millennium. Today it feels like the living, breathing part of Rome, where kids play football in the squares, the odd clanger of a modern building interrupts the skyline and rainbow-patterned peace flags flutter in the warm spring sun.

On face value Trastevere is all cobbled back streets, parmesan shops and dusty orange brick work. Down those back streets are patchworks of convent and monastery hiding behind high, painted walls. Dig a little deeper, or save time and get a guide for a morning, and you'll find some beautiful and bizarre relics behind the unassuming walls.

The church of Santa Cecilia is a case in point. It is home to an exquisite marble sculpture of the saint herself, reputedly modeled on the pose in which she died in the fifth century, a martyr, her neck slit by religious zealots. Santa Cecilia's body was not discovered until 1599 - but being a saint, it was entirely preserved.

Flash a few euros at the small round nun in the entrance and you not only get a smile, but access to the convent, and galleries with views of the church interior through metal grids designed to keep the nuns hidden from Joe Public. She'll also show you the only surviving Cavanelli fresco. Giotto's closest contemporary's last painting was protected by wooden panels until they were removed for cleaning in the 1920s. Elsewhere in the church his mosaics feature thousands of tiny gold tablets, each made from a leaf of gold intricately sandwiched between two sheets of glass.

Next door is the church of St Francesco a Ripa, where a caretaker will (for a few more euros) take you up some narrow winding stairs and into the little cell of St Francis - believed to have been where the original Benedictine monk slept. The stone he used as a pillow - following the "discomfort equals closer to god" theory - is still there. And so is a 18th-century baroque altar made of walnut, which at the twiddling of a knob rotates to reveal gold frames containing, literally, the fingers and toes of holy people.

We saw all this on a day's walking tour with Maria Teresa (or Fact Woman, as she came to be known). It was my first walking tour and quite an education, initially in a learning way, but by the end of the day in the way that school used to make me want to run away and be rude to the teachers. Nevertheless, with all the gems she showed us, it was well worth seven hours of relentless information. The sites are, of course, very religious (I'm not) but the drama of the scenes depicted in every church was enough to captivate me. Fact Woman explained that the Roman churches used dramatic images of women in the throes of death, arching their backs in ecstasy at being reunited with God, to try and engage Romans, to make it all a bit more interesting. The EastEnders of their day, the Trastevere sites managed to distract me from mooching for a whole day.

But mooching and people watching remained the main theme. From my hotel, which inexplicably had a goldfish in a jug and a small bowl of cherry tomatoes in reception, there was a view of the San Francisco monastery's backyard. In the courtyard outside my bedroom bells rang regularly and monks strolled around in leather sandals. All very authentic but, this being Trastevere, there was also a cement mixer and some beer crates. The hotel's roof garden was well worth a visit for its 360-degree views of Rome and its surrounding hills, which themselves provide some of the best vistas of Rome and are well worth the climb.

We ate in some classy restaurants in town, often billed as "the place to be seen", but they didn't have the same simplicity of the marinated vegetables and pecorino and pepper pasta that I fell deeply in love with in Trastevere's trattorias. White chocolate ice cream with an espresso thrown over summed up my new-found Italian food theory: order the dishes with the least ingredients - they are so good they don't need any frills.

So I didn't see the Vatican - I did see the Colosseum, twice, from cabs - but in Trastevere I got rosy cheeks, four pounds in weight, a taste for bizarre religious relics and a lovely vintage leather handbag.

· Polly Curtis travelled to Rome with Thomson Cities and British Airways. Thomson Cities offers two-night breaks to Rome staying at the San Francesco hotel from £311 per person (£342 for three nights). The price, valid for travel from July 1 - August 31, includes bed and breakfast accommodation based on two people sharing a twin/double room, return scheduled flights from London Heathrow with British Airways, all taxes and a guidebook. British Airways runs five daily services to Rome from London Heathrow.

· For reservations call 0870 606 1476, or consult www.thomsoncities.co.uk

· For further information on the San Francesco consult www.hotelsanfrancesco.net