Q. 1. Why is it that there is a Catholic Cathedral in most large cities?------------
A. 1. First of all, it should be understood that the word "Cathedral" has its roots from the word "Cathedra." "Cathedra" is a Greek word for chair, designating the chair or seat of a bishop in the principal church of his diocese, which is therefore called a cathedral. So when you see a Catholic Cathedral, it is to be understood that there is a Bishop who resides locally, overseeing his Diocese from that specific location.
The following article nicely explains the purpose of a Cathedral:
A CATHEDRAL: A CHURCH WITH A SPECIAL CHAIR
A Cathedral is the center of the life of the local Church. The very word "cathedral" in Latin or Greek, means "chair." From the cathedra, the chair or the seat, the Bishop teaches, sanctifies, and guides the people of God, the church. From the cathedral, the church with the bishop's chair, the Bishop oversees and safeguards the life of the Catholic people of a particular diocese.
Since the early Christian centuries, while seated in their chairs and facing their people, the bishops have preached the gospel of Christ to them. Respect for the chair, the cathedra, has always signified respect for the bishop and for his sanctifying and governing role, for his role as leader and witness to Christ the Good Shepherd.
There is a chair up for the bishop in every diocese, in every local church. From his chair the bishop gathers the people, like a shepherd bringing together a flock. He instructs, encourages, sometimes admonishes, but is always called to challenge them. It is here that the people drink of the rich reserves of the Catholic tradition. It is here that the mystery at the heart of the Catholic faith - the mystery of Christ himself present and active through the gift of the Spirit - is celebrated in its fullness. The cathedral church requires that it not only be a noble sacred space but also a noble sacred space that is large enough to gather large numbers of people for diocesan liturgical celebrations and events.
The Body of Christ, the Church, comes to a full stature when its members gather for prayer and worship together with their bishop, his presbyters, deacons, and other ministers at the altar, united to every local church in the world and to the Bishop of Rome, the Pope, as their head. It is here that the unity of the church becomes visible. This is the prime expression of the Church as one, holy, catholic and apostolic, the marks of the Church affirmed week by week as the Catholic people throughout the world profess the Creed together. Every bishop's ministry is to preserve communion - the bonds of faith over and below - among all those who come together at the Table of the Word and Sacrament as Christians have done since the time of the apostles.
A cathedral is above all, a house for the Church - church understood as the baptized people of God. It must b e a fitting place, worthy of the mysteries celebrated and received in it. It is to be high enough, lean and spare enough, so that the eye and the heart are lifted up to God. It is to be wide enough to welcome all who come, believers and unbelievers, people who belong to the Catholic community and those who don't. The cathedral is to invite all of us to a future full of hope and promise even while keeping our minds and hearts rooted in the truth that has been handed on to us from generation upon generation, like God's mercy rolling down through the ages.
[Source: St. Paul Cathedral, Saskatoon, SK, Canada; Parish Bulletin, June 7, 2009]