Having been the seat of the Catholic Church for so much of its history, it comes as no surprise that Rome is full of churches containing some of the most beautiful treasures, works of art and artifacts of the Christian world.
If you're coming to Rome with any interest in churches - or in art - some of the ones you should make sure of visiting are the Basilica of San Paolo, Santa Maria Maggiore and Santa Maria del Popolo. And that's before you even get started on the Vatican...
When you're caught up in the sightseeing, and being bustled to and fro by hundreds of other tourists with their cameras and their guidebooks, it can be easy to forget that the churches are also places of worship. If there's a service taking place while you're there, keep quiet and steer well clear of it. Some of the churches ask non-worshippers to avoid coming inside altogether during a service.
If you plan on entering a church (and you really should, as many of the most remarkable works of art in Rome are to be found inside churches), then prepare yourself by dressing conservatively. Avoid showing too much skin and ensure that both your shoulders and your knees are covered—this means no vest tops or shorts / short skirts, even in hot weather.