The official religious denomination of Italy is Roman Catholicism. Then what is Roman Catholicism? In history this is called the Western Church centering Rome as the headquarter. At that time, there is the Eastern Church that centers on the Jerusalem where the Western Church rooted. After that, the leaders of Eastern Church passed away so the western church developed their own church through the Bishops. Many people started to follow the teachings of the Eastern Church at that time.
Since the death of all the apostles and disciples of Jesus, many wavered and came to wander. At that time, Bishops started to mix the paganism in Rome in their teachings. Many Bishops opposed that but when Roman Emperor came to power, he abolished the Sabbath Day in 321 AD. After that, all the teachings of the Eastern Church disappeared one by one. Roman Church sat in power and controlled Rome which is called the Papacy-a kingdom ruled by Popes. This is now the birth of the Roman Catholics.
Since then, Roman Catholics accepted doctrines from different countries mixing it in their teaching. From AD 321, the church did not follow the teachings of the Eastern Church. In other words, the Roman Catholics had their own doctrines already since they lost all the teachings of the Eastern Church. The Roman Catholic spread their doctrines throughout the world. Italy is the center of Roman Catholicism. This is why through out the country, there are numerous Roman Catholic Churches that outwardly depict the arts and culture of the country.