When the group from Ravenna arrived, including Cornelius and his archdeacon Peter from Imola, Sixtus recognized Peter as the young man in his vision and consecrated him as a bishop.

After the murder in that year of Henry III of France, Pope Sixtus V sent Enrico Caetani as legate to Paris to negotiate with the Catholic League of France, and chose Bellarmine to accompany him as theologian.

Their family is notable for their bitter feud with the Orsini family over influence in Rome until it was stopped by Papal Bull in 1511 ; in 1571 the Chiefs of both families married nieces of Pope Sixtus V.

The church and monastery of San Pietro in Montorio originally belonged to the Celestines in Rome ; but they were turned out of it by Sixtus IV to make way for Franciscans, receiving from the Pope in exchange the Church of St Eusebius of Vercelli with the adjacent mansion for a monastery.

On 28 February 1476, Pope Sixtus IV, a Franciscan after whom the Sistine Chapel is named, authorized those dioceses that wished to introduce the feast to do so, and introduced it to his own diocese of Rome in 1477, with a specially composed Mass and Office of the feast.

In the 16th century Sixtus V bisected Bramante's Cortile del Belvedere with a cross-wing to house the Apostolic Library in suitable magnificence. The 16th and 17th centuries saw other privately endowed libraries assembled in Rome: the Vallicelliana, formed from the books of Saint Filippo Neri, with other distinguished libraries such as that of Cesare Baronio, the Biblioteca Angelica founded by the Augustinian Angelo Rocca, which was the only truly public library in Counter-Reformation Rome ; the Biblioteca Alessandrina with which Pope Alexander VII endowed the University of Rome ; the Biblioteca Casanatense of the Cardinal Girolamo Casanate ; and finally the Biblioteca Corsiniana founded by the bibliophile Clement XII Corsini and his nephew Cardinal Neri Corsini, still housed in Palazzo Corsini in via della Lungara. The Republic of Venice patronized the foundation of the Biblioteca Marciana, based on the library of Cardinal Basilios Bessarion. In Milan Cardinal Federico Borromeo founded the Biblioteca Ambrosiana.

This selection can be seen as a compromise between factions, Borgia and della Rovere, picking a frail cardinal with long experience in the Curia over the kin of either Sixtus IV or Alexander VI.

The name of Sixtus is often connected with a great building boom in Rome: Santa Sabina on the Aventine Hill was dedicated during his pontificate and he built Santa Maria Maggiore, whose dedication to Mary the Mother of God reflected his acceptance of the Ecumenical council of Ephesus which closed in 431.

The influence of his friends procured for him, from Pope Paul II ( 1464 – 71 ), the bishopric of Savona, and in 1473, with the support of Giuliano Della Rovere, later Pope Julius II, he was made cardinal by Pope Sixtus IV, whom he succeeded on 29 August 1484 as Pope Innocent VIII.

Giulliano della Rovere, as cardinal, age 34 ( left ) with uncle and patron Francesco della Rovere, Pope Sixtus IV ( right ).

His remains, along with those of his uncle, Pope Sixtus IV, were later desecrated during the Sack of Rome in 1527.

Sixtus continued a dispute with King Louis XI of France, who upheld the Pragmatic Sanction of Bourges ( 1438 ), according to which papal decrees needed royal assent before they could be promulgated in France.

Louis was thus in conflict with the papacy and Sixtus ( as a princely strategist himself ) could not permit it.

Pietro became one of the richest men in Rome and was entrusted with Sixtus IV's foreign policy.

The secular fortunes of the Della Rovere began when Sixtus invested his nephew Giovanni with the lordship of Senigallia and arranged his marriage to the daughter of Federico III da Montefeltro, duke of Urbino ; from this union came a line of Della Rovere dukes of Urbino that lasted until the line expired in 1631.

In his territorial aggrandizement of the Papal States, Sixtus IV's niece's son Cardinal Raffaele Riario, for whom the Palazzo della Cancelleria was constructed, was a leader in the failed " Pazzi conspiracy " of 1478 to assassinate both Lorenzo de ' Medici and his brother Giuliano and replace them in Florence with Sixtus IV's other nephew, Girolamo Riario.

To this, Sixtus IV replied with an interdict and two years ' of war with Florence.

Nevertheless, Sixtus IV quarrelled over protocol and prerogatives of jurisdiction, was unhappy with the excesses of the Inquisition and condemned the most flagrant abuses in 1482.

In 1475 he went to Rome to work with Pope Sixtus IV on calendar reform.

Sixtus IV ( 1471 – 1484 ) established the practice of selling indulgences to be applied to the dead, thereby establishing a new stream of revenue with agents across Europe.

* The four fountains ( Quattro Fontane ) with reclining river gods ( 1588 – 93 ) commissioned by Pope Sixtus V.

This discretion contributed not a little to his election to the papacy on 24 April 1585, with the title of Sixtus V. The story of his having feigned decrepitude in the conclave, in order to win votes, is pure invention.

Scarcely had the reprinting of the Talmud been begun, and the conditions of its printing been arranged by the commission, when Sixtus died.

Pope Sixtus IV is known for having built the Sistine Chapel, which is named for him.

Also in 1591, Gregory XIV modified the Apostolic Constitution Effraenatam of Pope Sixtus V ( 1588 ) so that the penalty for abortion did not apply until the foetus became animated.

The basis for this is because Pope Sixtus III's list of saints buried in St. Callistus ' Catacomb does not include Urban in the succession of Popes but rather in a list of foreign bishops.

For refusing to desist from the very hostilities that he himself had instigated ( and for being a dangerous rival to Della Rovere dynastic ambitions in the Marche ), Sixtus IV placed Venice under interdict in 1483.

The predecessor of the congregation was the Sacred Congregation for Rites, founded by Pope Sixtus V on 22 January 1588 in the Bull Immensa Aeterni Dei.

Pope Sixtus IV calls for a crusade to drive it away.

The ordinary income of the pope for the year 1517 had been reckoned at about 580, 000 ducats, of which 420, 000 came from the States of the Church, 100, 000 from annates, and 60, 000 from the composition tax instituted by Sixtus IV.

A visit to the villa of Cardinal Luigi d ' Este in 1573 convinced Pope Gregory XIII to start the building of a summer residence the following year, in an area considered healthier than the Vatican Hill or Lateran: His architects were Flaminio Ponzio and Ottaviano Nonni, called Mascherino ; under Pope Sixtus V, works were continued by Domenico Fontana ( the main facade on the Piazza ) and Carlo Maderno, and by Gian Lorenzo Bernini for Pope Clement XII.

Sixtus had, however, no appreciation of antiquities, which were employed as raw material to serve his urbanistic and Christianising programs: Trajan's Column and the Column of Marcus Aurelius ( at the time misidentified as the Column of Antoninus Pius ) were made to serve as pedestals for the statues of SS Peter and Paul ; the Minerva of the Capitol was converted into an emblem of Christian Rome ; the Septizonium of Septimius Severus was demolished for its building materials.

Sixtus excommunicated Henry of Navarre ( future Henry IV of France ), and contributed to the Catholic League, but he chafed under his forced alliance with Philip II of Spain, and looked for escape.

Sixtus is noted for developing the Roman Catholic Church's teaching on contraception and abortion.

The concessions given in them were confirmed by bulls issued by Pope Callixtus III ( Inter Caetera quae in 1456 ), Sixtus IV ( Aeterni regis in 1481 ), and Leo X ( 1514 ), and they became the models for subsequent bulls issued by Pope Alexander VI: Eximiae devotionis ( 3 May 1493 ), Inter Caetera ( 4 May 1493 ) and Dudum Siquidem ( 23 September 1493 ), in which he conferred similar rights to Spain relating to the newly-discovered lands in the Americas.

After his death Sixtus IV and a selected group of cardinals inspected the treasure laid up against expenditures against the Turks: they found 54 silver shells filled with pearls, to a value of 300, 000 ducats, jewels and gold intended for refashioning, worth another 300, 000 ducats, and a magnificent diamond worth 7, 000 ducats, which was sent to Cardinal d ' Estouteville to cover monies he had advanced to the pontiff.

Pope Sixtus V ( 1585 – 1590 ) planned to turn the building into a wool factory to provide employment for Rome's prostitutes, though this proposal fell through with his premature death.

These paintings were completed in 1482, and on 15 August 1483, Sixtus IV celebrated the first mass in the Sistine Chapel for the Feast of the Assumption, at which ceremony the chapel was consecrated and dedicated to the Virgin Mary.

According to a communication from Andreas of Trebizond to Pope Sixtus IV, by the time of its demolition to make way for the present chapel, the Cappella Maggiore was in a ruinous state with its walls leaning.

The present chapel, on the site of the Cappella Maggiore, was designed by Baccio Pontelli for Pope Sixtus IV, for whom it is named, and built under the supervision of Giovannino de Dolci between 1473 and 1481.

As a reward, Sixtus IV granted the Pazzi monopoly at the alum mines at Tolfa — alum being an essential mordant in dyeing in the textile trade that was central to the Florentine economy — and he assigned to the Pazzi bank lucrative rights to manage Papal revenues.

Pope Sixtus IV commissioned Signorelli to paint some frescoes, now mostly very dim, in the shrine of Loreto — Angels, Doctors of the Church, Evangelists, Apostles, the Incredulity of Thomas and the Conversion of St Paul.

* 1590: Pope Sixtus V — Pope Urban VII — Pope Gregory XIV

With new access streets installed by Sixtus IV — Via Florea and Via Pellegrino — the square became a necessary corridor for important people passing between the Basilica of St. John Lateran and the Vatican, thus bringing wealth to the area: a flourishing horse market took place twice a week ( Monday and Saturday ) and a lot of inns, hotels and shops came to be situated in Campo de ' Fiori.