Basilica of St. John Lateran
The Basilica of St. John Lateran — in Italian, the Basilica di San Giovanni in Laterano — is the cathedral church of Rome and the official ecclesiastical seat of the Pope. Officially named Archibasilica Sanctissimi Salvatoris (Archbasilica of the Most Holy Savior), it is the oldest and ranks first among the five major basilicas, and holds the title of ecumenical motherchurch among Catholics.
An inscription on the façade, Christo Salvatore, dedicates the Lateran as Archbasilica of the Most Holy Saviour, for all patriarchal basilicas are dedicated to Christ himself. As the cathedral of the Bishop of Rome, containing the papal throne (Cathedra Romana), it ranks above all other churches in the Catholic Church, even above St. Peter's Basilica in the Vatican.

Lateran Palace
The site on which the Basilica sits was occupied during the Early Empire by the palace of the gens Laterani. The Laterani served as administrators for several emperors; Sextius Lateranus was the first plebeian to attain the rank of consul. One of the Laterani, Consul-designate Plautius Lateranus, became famous for being accused by Nero of conspiracy against the emperor. The accusation resulted in the confiscation and redistribution of his properties.
The Lateran Palace fell into the hands of the emperor when Constantine married his second wife Fausta, sister of Maxentius. Known by that time as the "Domus Faustae" or "House of Fausta," the Lateran Palace was eventually given to the Bishop of Rome by Constantine. The actual date of the gift is unknown but scholars believe it had to have been during the pontificate of Pope Miltiades, in time to host a synod of bishops in 313 that was convened to challenge the Donatist schism, declaring Donatism as heresy. The palace basilica was converted and extended, eventually becoming the cathedral of Rome, the seat of the popes as patriarchs of Rome.
The official dedication of the Lateran Palace and basilica was presided by Pope Sylvester I in 324, declaring both as Domus Dei or "House of God." In reflection of the basilica's primacy in the world as mother church, the words Sacrosancta Lateranensis ecclesia omnium urbis et orbis ecclesiarum mater et caput are incised across the façade, meaning "Most Holy Lateran Church, of all the churches in the city and the world, the mother and head."
Twice the Lateran Palace and basilica have been rededicated. Pope Sergius III dedicated them to Saint John the Baptist in the 10th century in honor of the newly consecrated basilica baptistry. Pope Lucius II dedicated the Lateran Palace and basilica to Saint John the Evangelist in the 12th century. The church became the most important shrine in honor of the two saints, not often jointly venerated (but see Peruzzi Chapel, Santa Croce, Florence). In later years, a Benedictine monastery was established at the Lateran Palace, devoted to serving the basilica as a devotional to the two saints.
Every pope since Miltiades occupied the Lateran Palace until the reign of the French Pope Clement V, who in 1309 decided to transfer the official seat of the Church to Avignon, a papal fief that was an enclave within France. During the Avignon papacy, the Lateran Palace and the basilica began to decline. Two destructive fires rampaged through the Lateran Palace and the basilica, in 1307 and again in 1361. In both cases, the Avignon papacy sent money to their bishops in Rome to cover costs in reconstruction and maintenance. Despite the action, the Lateran Palace and the basilica lost its former splendor.
When the Avignon papacy formally ended and the Bishop of Rome again resided in Rome, the Lateran Palace and the basilica were deemed inadequate considering the accumulated damage. The popes took up residency at the Basilica di Santa Maria in Trastevere and later at the Basilica di Santa Maria Maggiore. Eventually, the Palace of the Vatican was constructed, and the papacy moved in; the papacy remains there today.
Pope Sixtus V tore down the original Lateran Palace and basilica and commissioned replacements. The rebuilt Lateran Palace and the Basilica di San Giovanni in Laterano became separate entities. Today the Lateran Palace is home to the Pontifical Museum of Christian Antiquities.
The square in front of the Lateran Palace has a red granite obelisk, the largest in the world, erected by Tuthmosis III in Karnak. It was removed to Rome by Constantius in 357 and re-erected in the Circus Maximus. Sixtus V had it re-erected in 1587 on its present site.
The Lateran Palace has also been the site of five Ecumenical councils. See Lateran councils.

Reconstruction
There were several attempts at reconstruction of the basilica before Pope Sixtus V's definitive project. Sixtus hired his favorite architect Domenico Fontana to oversee much of the project. Further renovation of the interior ensued under the direction of Francesco Borromini, commissioned by Pope Innocent X. The vision of Pope Clement XII for reconstruction was an ambitious one: he launched a competition to design a new façade. The winner of the competition was Alessandro Galilei. The façade as it appears today was completed in 1735. Galilei's façade however removed all vestiges of traditional ancient basilica architecture.

Architectural history
An apse lined with mosaics and open to the air still preserves the memory of one of the most famous halls of the ancient palace, the "Triclinium" of Pope Leo III, which was the state banqueting hall. The existing structure is not ancient, but it is possible that some portions of the original mosaics have been preserved in a three-part mosaic: in the centre Christ gives their mission to the Apostles, on the left he gives the keys to St. Sylvester and the Labarum to Constantine, while on the right St. Peter gives the papal stole to Leo III and the standard to Charlemagne.
Some few remains of the original buildings may still be traced in the city walls outside the Gate of St. John, and a large wall decorated with paintings was uncovered in the 18th century within the basilica itself, behind the Lancellotti Chapel. A few traces of older buildings also came to light during the excavations made in 1880, when the work of extending the apse was in progress, but nothing was then discovered of real value or importance.
A great many donations from the popes and other benefactors to the basilica are recorded in the Liber Pontificalis, and its splendour at an early period was such that it became known as the "Basilica Aurea", or Golden Basilica. This splendour drew upon it the attack of the Vandals, who stripped it of all its treasures. St. Leo the Great restored it about 460, and it was again restored by Pope Hadrian, but in 896 it was almost totally destroyed by an earthquake— ab altari usque ad portas cecidit "it collapsed from the altar to the doors"— damage so extensive that it was difficult to trace the lines of the old building, but these were in the main respected and the new building was of the same dimensions as the old. This second church lasted for four hundred years and then burnt in 1308. It was rebuilt by Pope Clement V and Pope John XXII, only to be burnt down once more in 1360, but again rebuilt by Pope Urban V.
Through these various vicissitudes the basilica retained its ancient form, being divided by rows of columns into aisles, and having in front a peristyle surrounded by colonnades with a fountain in the middle, the conventional Late Antique format that was also followed by the old St Peter's. The façade had three windows, and was embellished with a mosaic representing Christ, the Saviour of the World. The porticoes were frescoed, probably not dating further back than the twelfth century, commemorating the Roman fleet under Vespasian, the taking of Jerusalem, the Baptism of the Emperor Constantine and his "Donation" of the Papal States to the Church. Inside the basilica the columns no doubt ran, as in all other basilicas of the same date, the whole length of the church from east to west, but at one of the rebuildings, probably that which was carried out by Clement V, the feature of a transverse nave was introduced, imitated no doubt from the one which had been, long before this, added at Basilica of Saint Paul Outside the Walls. It was probably at this time also that the church was enlarged.
Some portions of the older buildings still survive. Among them the pavement of medieval Cosmatesque work, and the statues of St. Peter and Saint Paul, now in the cloisters. The graceful baldacchino over the high altar, which looks so utterly out of place in its present surroundings, dates from 1369. The stercoraria, or throne of red marble on which the popes sat, is now in the Vatican Museums. It owes its unsavoury name to the anthem sung at the papal enthronement, "De stercore erigens pauperem" ("lifting up the poor out of the dunghill", from Psalm 112). From the fifth century there were seven oratories surrounding the basilica. These before long were incorporated in the church. The devotion of visiting these oratories, which held its ground all through the medieval period, gave rise to the similar devotion of the seven altars, still common in many churches of Rome and elsewhere.
Of the façade by Alessandro Galilei (1735), the cliché assessment has ever been that it is the façade of a palace, not of a church. Galilei's front, which is a screen across the older front creating a narthex or vestibule, does express the nave and double aisles of the basilica, which required a central bay wider than the rest of the sequence; Galilei provided it, without abandoning the range of identical arch-headed openings, by extending the central window by flanking columns that support the arch, in the familiar Serlian motif. By bringing the central bay forward very slightly, and capping it with a pediment that breaks into the roof balustrade, Galilei provides an entrance doorway on a more-than-colossal scale, framed in the paired colossal Corinthian pilasters that tie together the façade in the manner introduced at Michelangelo's palace on the Campidoglio.

Lateran cloister
Between the basilica and the city wall there was in former times the great monastery, in which dwelt the community of monks whose duty it was to provide the services in the basilica. The only part of it which still survives is the cloister, surrounded by graceful columns of inlaid marble. They are of a style intermediate between the Romanesque proper and the Gothic, and are the work of Vassellectus and the Cosmati. This beautiful cloister dates to the early 13th century.

Lateran baptistry
The octagonal Lateran Baptistry stands somewhat apart from the basilica. It was founded by Pope Sixtus III, perhaps on an earlier structure, for a legend grew up that Constantine the Great had been baptized there and enriched the structure. (He was actually baptised in the East, by an Arian bishop.) This baptistry was for many generations the only baptistery in Rome, and its octagonal structure, centered upon the large basin for full immersions provided a model for others throughout Italy, and even an iconic motif of illuminated manuscripts, "The fountain of Life".

Catholic liturgy
On the liturgical calendar of the Catholic Church, November 9 is the feast of the Dedication of the Basilica of St. John Lateran.