When people visit Rome in pilgrimage to Roman churches, one of the first places where they want to go to is Saint Peter’s Basilica. And there are certainly good reasons for that: the monumentality of the place, the proximity to Vatican museums, the Pope living very close to the Basilica, the outstanding art that is displayed inside, the dome, and so on and so forth. But not many know that Saint Peter’s Basilica is not the Cathedral of the Pope. When a Pope is elected he has to take possession of his own Basilica, where his Episcopal chair is (cathedra, in Latin, so the name “Cathedral”), and this Basilica is Saint John Lateran. Because we are starting to look at the four major Basilicas in Rome first, we need to understand what this term means. “The name derives from the Latin term basilica, which in turn derives from the Greek βασιλική (phonetically basilikè), a word meaning ‘regal’ and which is an ellipse of the complete expression basilikè oikìa, which means ‘regal house.’ This type of building originally served for large-scale commercial transactions, and at the same time it was like a court of law. Its origins date back to the era of the Republic of Rome (between 509 and 27 BC). Over time, various structural changes have taken place which later became canonical. It will be the plant that the early Christian religious buildings will adopt” (https://it.aleteia.org/2014/11/19/cosa-significa-basilica-da-dove-viene-questa-parola/). So a “Basilica” is a very spacious religious building, but not all spacious religious buildings are basilicas.
Saint John Lateran is defined as the Mater and Caput of all churches in Rome and throughout the world. It was built on the Caelian Hill (one of the seven Hills of Rome) on a land that was owned by the Laterani family, a wealthy Roman family that fell in disgrace under emperor Nero in the first century. After some events that we are not mentioning here, the land will be owned by a certain Fausta, who for some historians was the second wife of emperor Constantine (280-337), the emperor that will free Christianity and other religions from persecution with the edict of Milan in 313. So Constantine need to provide also for spaces where the Christians can celebrate their worship and to this end he will donate the land of the Domus Faustae to Pope Melchiades.
The Basilica was consecrated in 318 and dedicated to the Most Holy Savior. In the 9th century Pope Sergius III also dedicated the Basilica to Saint John the Baptist and in the 12th century was added also Saint John the Evangelist by Pope Lucius II. So the Basilica celebrates both Saint John the Evangelist and Saint John the Baptist. The church witnessed several historical events, as for example the decline under the so called “Avignon captivity,” when the seat of Peter was moved from Rome to France in the 14th century. But in the centuries thereafter the Popes will show their care for their Cathedral, promoting works of restoration and enriching the church with beautiful works of art. We cannot forget to mention the work done by Francesco Borromini in the Baroque period, for the restoration of the Basilica: “The archaeologist Fioravante Martinelli (1599-1667), a Hebrew and Latin writer from the Vatican Apostolic Library, maintains that Borromini’s choice depended on the delicacy of the restoration work as well as the fame he enjoyed, therefore praised him in his Roma ricercata nel suo sito, many times reprinted, and in his Primo trofeo, enhancing the work of Borromini renewal of the Arcibasilica. To all this must be added the problem of the narrowness of the times: at the beginning of 1646 the Pope had not only had the Borrominian design, now in the Latin Vatican code 11.258 / 166-, but the works had been started in April 1646. The restoration was to be ready for the opening of the 1650 jubilee and Borromini succeeded, as evidenced by the commemorative plaques scattered throughout the Arcibasilica. The Borrominian works, limited by the pontiff to the five naves, lasted from May 1646 to October 1649, resumed on February 20, 1652 for the renovation of the floors of the minor naves entrusted to Luca Berrettini, Giovanni Martino and Filippo Frugone. The floor of the central nave was restored by Pier Santi Ghetti. Innocent x, on 21 January 1653, assigned 12 columns of ancient green, replaced by pillars, to the church of S. Agnese in Agone that he was building. The Pope, in this same year, ordered the restoration of the porch and the floor.” (http://www.vatican.va/various/basiliche/san_giovanni/it/basilica/navata.htm).
The Basilica is managed by an Archpriest, usually a Cardinal, who is the Vicar of the Pope for the diocese of Rome. It is visited by many pilgrims and tourists and is the place where the liturgies that are more proper to the Diocese of Rome take place, often presided by the Archpriest in the name of the Pope.