The church contains works by several famous artists, such as Raphael, Gian Lorenzo Bernini, Caravaggio, Alessandro Algardi, Pinturicchio, Andrea Bregno, Guillaume de Marcillat and Donato Bramante.

The well-known foundation legend of Santa Maria del Popolo revolves around the evil memory of Emperor Nero and the cleansing of the area from this malicious legacy by Pope Paschal II.

The sepulchre was later buried under a landslide and on its ruins grew a huge walnut tree that ″was so tall and sublime that no other plant exceeded it in any ways.″ The tree soon became the haunt for a multitude of vicious demons harassing the inhabitants of the area and also the travelers arriving in the city from the north through Porta Flaminia: ″some were being frightened, possessed, cruelly beaten and injured, others almost strangled, or miserably killed.″ As the demons endangered an important access road of the city and also upset the entire population, the newly elected pontiff, Paschal II, was seriously concerned.

He ″saw the flock of Christ committed to his watch, becoming prey to the infernal wolves.″[1] The Pope fasted and prayed for three days and at the end of that period, exhausted, he dreamt of the Blessed Virgin Mary, who gave him detailed instructions on how to free the city from the demonic scourge.

On the Thursday after the Third Sunday of Lent in 1099, the Pope organised the entire clergy and populace of Rome in one, impressive procession that, with the crucifix at its head, went along the urban stretch of the Via Flaminia until it reached the infested place.

The cardinal convened a meeting to Santa Maria del Popolo for the delegates of the hermitic communities where they declared their union and the foundation of the new order that the Pope confirmed with the bull Pia desideria on 31 March 1244.

The so-called Grand Union that integrated various other hermitic communities with the Tuscans by the order of Pope Alexander IV was also established on the general chapter held in Santa Maria del Popolo under the supervision of Cardinal Annibaldi in March 1256.

Giorgio Vasari in his Lives attributed all the important papal projects in Rome during Sixtus IV to a Florentine, Baccio Pontelli including the basilica and monastery of Santa Maria del Popolo.

Modern researchers deemed this claim highly dubious and proposed other names among them Andrea Bregno, a Lombard sculptor and architect whose workshop certainly received important commissions in the basilica.

Julius II granted assent to the wealthy Sienese banker, Agostino Chigi, who was adopted into the Della Rovere family, to build a mausoleum replacing the second side chapel on the left in 1507.

The pope launched his first campaign here on 26 August 1506 and when he returned to Rome after the successful Northern Italian war, he spent the night of 27 March 1507 in the convent of Santa Maria del Popolo.

This was shown on 23 November 1561 when Pope Pius IV held a solemn procession from St. Peter's to the Basilica of Santa Maria del Popolo on the occasion of reopening the Council of Trent.

In April 1594 Pope Clement VIII ordered the removal of the tomb of Vannozza dei Cattanei, the mistress of Alexander VI, from the basilica because the memory of the Borgias was a stain on the history of the Catholic Church for the reformed papacy and all the visible traces had to disappear.

During the first half of the 17th century there were no other significant building works in the basilica but many Baroque funeral monuments were erected in the side chapels and the aisles, the most famous among them the tomb of Cardinal Giovanni Garzia Mellini by Alessandro Algardi from 1637 to 1638.

The urban setting of the basilica changed fundamentally between 1816 and 1824 when Giuseppe Valadier created the monumental Neo-Classical ensemble of Piazza del Popolo, commissioned by Pope Pius VII.

The frieze has a fine carved decoration of artificial foliage, pecking birds and three putti who are holding torches and oak branches in their hands and carrying bowls of fruit on their heads.

The central motif is the Madonna del Popolo surrounded by the symbols of heavenly light and paradisiacal abundance, intertwined with the emblem of the Della Rovere dynasty, and set in a perfectly classical frame.

The plain pediment was originally decorated with the coat of arms of Pope Sixtus IV hanging on an acanthus leaf scroll corbel but only the truncated upper part of the shield survived.

With the first one, dated on 7 September 1472, which begins with the words Ineffabilia Gloriosae Virginis Dei Genitricis, he granted plenary indulgence and remission of all sins to the faithful of both sexes who, truly repented and confessed, attend this church on the days of the Immaculate Conception, Nativity, Annunciation, Visitation, Purification, and Assumption of the Blessed Virgin Mary.

[30] On both side of the right door there are smaller plaques commemorating the indulgences that Gregory XIII conceded to the basilica in 1582 and the fact that Sixtus V included Santa Maria del Popolo among the seven pilgrimage churches of Rome in 1586.

The original 15th-century architecture was largely preserved by Bernini who only added a strong stone cornice and embellished the arches with pairs of white stucco statues portraying female saints.

The statues were probably designed by Bernini himself, and a supposedly autograph drawing for the figure of Saint Ursula survived in the collection of the Museum der bildenden Künste in Leipzig, but his plans were executed by the sculptors of his workshop between August and December 1655.

The side altars are edicules made of different coloured marbles, they are embellished with triangular pediments, Corinthian pilasters, Classical friezes with acanthus scrolls and flanking angels.

The chalice on the Holy Family painting alludes to priesthood, the vocation of the cardinal, while the theme of the Visitation is strongly connected to fertility, something that was expected of the prince who married Maria Virginia Borghese in 1658, the date on the inscriptions, and founded the Roman branch of the Chigi dynasty.

The organ in the right transept was originally built in 1499–1500 by Stefano Pavoni, magister organorum from Salerno; its case was decorated with the coat of arms of Pope Alexander VI who probably contributed to the expenses.

Bernini designed two elegant marble cantorie for the instruments which are supported by stucco angels and putti displaying rich garlands of flowers and the coats of arms of Pope Alexander VII.

For the beauty of its paintings, the preciousness of marble revetments covering its walls and the importance of the artists involved in its construction the chapel is regarded one of the most significant sacral monuments erected in Rome in the last quarter of the 17th century.

The highlights of the chapel are the great fresco of the Madonna and Child Enthroned with Saints Augustine, Francis, Anthony of Padua and a Holy Monk above the altar, the Assumption of the Virgin Mary on the first wall and the illusionistic monochrome decoration of the pedestal with painted benches and martyrdom scenes.

The tomb of Giovanni Battista Gisleni, an Italian Baroque architect and stage designer who worked for the Polish royal court during the years 1630–1668, is probably the most macabre funeral monument in the basilica.

[43] One of the most important Mannerist funeral monuments in the basilica is the tomb of Cardinal Gian Girolamo Albani, an influential politician, jurist, scholar and diplomat in the papal court in the last decades of the 16th century.