Much like the rest of Italy, Rome is predominantly Christian, and the city has been an important centre of religion and pilgrimage for centuries, the base of the ancient Roman religion with the pontifex maximus and later the seat of the Vatican and the pope. Before the arrival of the Christians in Rome, the Religio Romana (literally, the "Roman Religion") was the major religion of the city in classical antiquity. The first gods held sacred by the Romans were Jupiter, the Most High, and Mars, the god of war, and father of Rome's twin founders, Romulus and Remus, according to tradition. Other deities such as Vesta and Minerva were honoured. Rome was also the base of several mystery cults, such as Mithraism. Later, after St Peter and St Paul were martyred in the city, and the first Christians began to arrive, Rome became Christian, and the Old St. Peter's Basilica was constructed in 313 AD. Despite some interruptions (such as the Avignon papacy), Rome has for centuries been the home of the Roman Catholic Church and the Bishop of Rome, otherwise known as the Pope.