Which cities were the leaders of the two Christian religions?

Answer 1

There is only one Christian religion; there are many Christian denominations.

The head of the Catholic denomination is the Pope, and he lives in Rome.

The formal head of the Church of English is the Queen, and she lives in London, and elsewhere in England; the "spiritual" head of the Church of English is the Archbishop of Canterbury.

The head of the Greek Orthodox Church is the Greek Ecumenical Patriarch, and he lives in Istanbul (formerly Constantinople).

The heads of the other Orthodox churches are located in their own cities, depending on the national focus of the church.

Most of the other denominations do not have a fixed city in which the head of their denomination lives.

Some denominations do not have a head person, but there is a sense of shared leadership.

Additional Comments:

Perhaps the questioner is referring to the time of two Popes in Western Europe (Catholic). Known as the 'Great Schism,' it began on September 20, 1378 with the election of Clement VII in Avignon, France. He was the second pope elected by the same college of cardinals in six months, and for the first time in history there were two "legitimate" claimants to be head of the church in Rome.