"On this rock I will build my Church"
Dear Brothers and Sisters,
The history behind our Cathedral! "Cathedra" literally means the established seat of the Bishop, placed in the mother church of a diocese which for this reason is known as a "cathedral"; it is the symbol of the Bishop's authority and in particular, of his "magisterium", that is, the evangelical teaching which, as a successor of the Apostles, he is called to safeguard and to transmit to the Christian Community. This is a very ancient tradition, proven to have existed in Rome since the fourth century through the mission entrusted to the Apostle Peter and his Successors.
When a Bishop takes possession of the particular Church that has been entrusted to him, wearing his mitre and holding the pastoral staff, he sits on the cathedra. From this seat, as teacher and pastor, he will guide the journey of the faithful in faith, hope and charity.
So what was the "Chair" of St Peter? Chosen by Christ as the "rock" on which to build the Church (cf. Mt 16: 18), he began his ministry in Jerusalem, after the Ascension of the Lord and Pentecost. The Church's first "seat" was the Upper Room, and it is likely that a special place was reserved for Simon Peter in that room where Mary, Mother of Jesus, also prayed with the disciples.
Subsequently, the See of Peter was Antioch, a city located on the Oronte River in Syria, today Turkey, which at the time was the third metropolis of the Roman Empire after Rome and Alexandria in Egypt. Peter was the first Bishop of that city, which was evangelized by Barnabas and Paul, where "the disciples were for the first time called Christians" (Acts 11: 26), and consequently where our name "Christians" came into being. In fact, the Roman Martyrology, prior to the reform of the calendar, also established a specific celebration of the Chair of Peter in Antioch. From there, Providence led Peter to Rome. Therefore, we have the journey from Jerusalem, the newly born Church, to Antioch, the first centre of the Church formed from pagans and also still united with the Church that came from the Jews. Then Peter went to Rome, the centre of the Empire, the symbol of the "Orbis" - the "Urbs", which expresses "Orbis", the earth, where he ended his race at the service of the Gospel with martyrdom.
So it is that the See of Rome, which had received the greatest of honours, also has the honour that Christ entrusted to Peter of being at the service of all the particular Churches for the edification and unity of the entire People of God. The See of Rome, after St Peter's travels, thus came to be recognized as the See of the Successor of Peter, and its Bishop's "cathedra" represented the mission entrusted to him by Christ to tend his entire flock.
(source: Libreria Editrice Vaticana)