Today is the feast of the dedication of Rome's first basilica, St. John Lateran. It is part of the Rome experience to actually be able to attend Mass there on the very feast of its dedication.
It was dedicated in the 320s (I have heard two dates), before St. Peter's or St. Paul outside the walls, with the name "Church of the Redeemer." So why is it called St. John and what does Lateran mean? Here's the deal. Some of the land there belonged to a wealthy Roman family of the time whose name was Laterano. Then, at different points in history, the church was named for St. John the Baptist and for St. John the Evangelist. Their names (as well as their statues on either side of Christ) can be seen in the facade.
The cathedral has, through history, succombed to fire, an earthquake, and invading hordes. Each time it was destroyed it was rebuilt and received new names in the process.
As you enter through the front facade you pass a Latin inscription which says "the holy Lateran church, mother and head of all churches in the city and world." Why does it say this? Two main reasons. One is that the Lateran was the Vatican until the 1300s. It was the official Papal residence until the Avignon period when, for about 70 years in the 1300s, the Popes transferred their residence to France. After that, as the Lateran structures had become inhabitable, the Popes took up residence in the Vatican, where they have remained to the present day. The second reason, very connected with the first, is that St. John Lateran is the cathedral of Rome: it is the see of the bishop of Rome (the Pope). In fact, it still houses the offices for the diocese of Rome. St. Peter's is a mamoth basilica in the Vatican city-state, but it is not the official see of the bishop of Rome. Lateran, 1 - St. Peter's, 0.
Inside is a beautiful artistic portrayal of salvation history, or of God's intervention through history aimed at man's salvation. There are three levels (see photo immediately above, right) of decoration in the main body of the Church. The top level is a series of 12 paintings of Old Testament prophets. Below these are 12 frieze sculptures depicting, on the left side, scenes from the Old Testament which prefigured some moment in the life of Christ, depicted in the corresponding place on the right side. The two following photos depict, from the Old Testament the angel staying Abraham's hand when he was about to sacrifice his son, Isaac, who carried the wood up the mountain, and from the New Testament, Christ carrying the cross.
This is a bridge from old to new. Below these are the 12 impressive sculptures of the apostles and St. Paul, each with some emblem indicative of what they are known for. They were present at the Church's foundation and were the first followers of Christ who set the Church on its course. But there is yet a fourth level. As our gaze descends from the prophets, to the friezes, to the apostles, it finally reaches the floor upon which we stand. The fourth level is us. We are the heirs of this great history, of God's presence and action in human history. The Church's continuity and the realization of her mission now depend on us.
Historically, St. John Lateran is monumental for its Christian significance. Structurally, it is a marvel. Spiritually, it is a testimony of salvation history and is a fitting symbol of the Catholic Church herself, which has survived so many upheavels and struggles through the centuries, while continuing to offer mankind the surest means by which to reach heaven.