Roman Catholic
The Vatican is not a "who" it is a "what." The Vatican is an independent city-state surrounded by the city of Rome, Italy. It is the headquarters of the Catholic religion.
Italy has freedom of religion. Rome is the headquarters of the Catholic faith, which is a monotheistic religion, as are Judaism and Islam. In the time of the Roman empire until A.D.313, the state religion was polytheistic, i.e. many gods.
Christians were persecuted until Rome and Italy adopted the Christian Faith.
the religion in Italy is catholic because the pope lives in Rome
Constantinople was based on the Christian religion and Rome was against it.
Christianity was proclamed the official religion of the roman empire on 550ish a.c. It means that the emperors where christians from then (or needed to be nice with the christian god.)
The worldwide headquarters of the Catholic Church is the Vatican in Rome and is headed by the Pope. The 'headquarters' are in the Vatican city. This is inside Rome but it has its own government so it is not actually part of Rome.
In the Vatican City, Rome. The Vatican City State is the smallest independent country in the world and lies within the centre of the capital city of Italy, Rome.
Rome is mainly Christian; mainly Catholic, but just about all religions are represented there.
In Vatican City in Rome Italy!
I believe that the larget Christian church is the Basilica at Vatican City in Rome, Italy.
Since the headquarters of the Catholic Church is the Vatican, and the Vatican is located in Rome, you could say that there are a lot of Christians in Rome right now.