Roma. The Eternal City. The Seat of Holy Mother Church.

For no one can be in doubt, indeed it was known in every age that the Holy and Most Blessed Peter, Prince and Head of the Apostles, the Pillar of Faith and the Foundation of the Catholic Church, received the Keys of the Kingdom from our Lord Jesus Christ, the Saviour and Redeemer of the human race, and that to this day and for ever he lives and presides and exercises judgment in his successors the Bishops of the Holy Roman See, which he founded and consecrated with his blood.

-From the speech of Philip, the Roman legate, at the 3rd session of the council of Ephesus, quoted by the First Vatican Council in the First Dogmatic Constitution on the Church of Christ.

The Pope, and those members of his court (the Roman Curia) to whom he delegates, rule the Church from Rome. Though the Papal Court has been temporarily relocated at times (most notably to Avignon), the Pope has always been the Bishop of Rome.