St. Mary Major stands slightly elevated with respect to the street layout of the Esquiline district and, in addition to being a station in the Pilgrimage of the Seven Churches , it is one of the six papal basilicas of Italy, which are of particular importance within the Catholic Church. Most likely founded in the 5th century by Pope Sixtus III, it is the only one of the great Roman basilicas to preserve the original early Christian structure, divided into three naves separated by 36 columns. The precious mosaics that can be admired in the nave also date back to the 5th century: the frieze decorating the trabeation, the 36 panels above it and the mosaic decorating the triumphal arch.
The basilica also contains remarkable works from later periods. The grandiose mosaic in the apse, created by Jacopo Torriti (1295) and depicting the "Coronation of Mary", and the frescoes of the prophets in the transept, attributed to Pietro Cavallini, Cimabue or the young Giotto, date back to the 13th century.
Three chapels house the tombs of illustrious individuals. Opened at the end of the 16th century, the Sistine Chapel of St. Mary Major preserves the remains of Popes Sixtus V and St. Pius V; opposite and aligned with the Sistine Chapel, the Pauline or Borghese Chapel, dating from the early 17th century, contains the tombs of Clement VIII and Paul V, surmounted by frescoes by Guido Reni. In the later Sforza Chapel (1564-73), designed by Michelangelo and built by Tiberio Calcagni and Giacomo Della Porta, high-ranking prelates are laid to rest.
The 75-metre-high bell tower of the basilica retains its 14th-century Romanesque appearance and is connected with a peculiar custom of ringing a few bells every evening at 9:00 pm: this custom originated in the 16th century when, according to legend, a mysterious bell began ringing outside the canonical time to call out to a pilgrim who had strayed from the streets of Rome. For this reason, the bell itself is referred to "the Lost One".