Devotion and pilgrimage rose to great levels, and in 1469 the construction of a basilica was ordered by Pope Paul II, and the greatest architects of the time - Ponticelli, Bramante, Sansovino, Giuliano da Sangallo - worked on the project. Recent studies focus on the hypotesis of a transportation by sea devised by human agency.
Three different architectural units are encased one inside the other: the outside basilica, the marble mausoleum inside, which surrounds the Holy House; the Holy House.
The basilica: the facade was completed in 1587, all in Istrian stone, with 3 huge bronze doors, built for the jubilee of the year 1600 in the foundry of Recanati, representing biblical subjects. The central door is the work of Antonio di Girolamo Lombardo, assisted by his brothers Pietro, Paolo e Giacomo. Along the square where the basilica rises is the two-floor Apostolic Palace begun in 1498 on a design by Donato Bramante. Another unique monument is the Fountain in the middle of the square, designed by arlo Maderno and his uncle Giovanni Fontana(1604 - 1614), with water brought through a 5-km-long gallery as a relief for the pilgrims. Anether true jewel is the Bell-tower, designed by Luigi Vanvitelli, and built betweem 1750 and 1755, which houses nine bells, one of which, called "Loreta" was made by Bernardo da Rimini in 1515, has a diameter of 184 cm and a weight of 7300 kilos.
The interior in the Gothic style is 93 mt long and 60 wide, ends in an octagonal dome under which is the original Nazareth house, inside a majestic mausoleum designed by Bramante. The dome was completed in the year 1500, by Giuliano da Sangallo, and shows the Brunelleschi influence as well as architect Sangallo's experience in military architecture. The dome was frescoed by Maccari (1890-1907) with themes from the Litany of Loreto and the history of the Immaculate Conception dogma.
The interior is divided into 3 naves with twelve chapels, six on each side, each a very special work of art and worship. The most important is the first chapel along the left nave, with a bronze baptismal font by Tiburzio Vergelli (1600-1607) and paintings by Cristoforo Roncalli, called Pomarancio (1605-1610), Pomarancio on the vault, representing ten stories from the life of the Madonna, six prophets and six Sibyls; then the Chapel of the Crucifix, with a wooden crucifix by Innocenzo da Petralia (1637) and frescoes by Biagetti (1928-1932); the French Chapel, closed by a delicate wrought-iron railing by E. Mattaccotta, contains paintings by Lameire (1896-1912) representing episodes from the life of St. Louis IX and the battle of the Knights Templar defending Nazareth, to the left; the Slavic Chapel with an altar triptych by S. De Witten and frescoes by Biagetti representing episodes from the lives of Saints Cyril and Methodius; the American Chapel with a mosaic by Baccio della Porta and frescoes by G. Steffanina (1970); the Polish Chapel with an altar triptych by A. Gatti and frescoes representing the victory of Sobiesky at Vienna and the battle of the Vistula; the Spanish Chapel with a bas-relief by Eduard Barron Gonzales of Castilla and frescoes by M.Faustini representing scenes from the life of the Holy Family; the Swiss Chapel with a mosaic by Angelica Kauffmann representing Mary's family (Ann and Joachim) and frescoes by C.Donati (1938) with scenes from the life of child Mary. In the Sacristy of St. John are 15th-century frescoes by Luca Signorelli, representing in the vault 8 angels followed by the Gospel-writers and Fathers of the Church, and below St. Paul on the road to Damascus, Christ and the Apostles. The Chapel of the Dukes of Urbino was committed by Guidobaldo II and Francesco Maria II della Rovere and contains a mosaic by F.Barrocci representing the "Annunciation" and wall frescoes by F.Zuccari representing the Betrothal, the Visitation, the Transitus, the Assumption, and the Coronation of Mary. In the Sacristy of St. Mark are 15th century frescoes by Melozzo da Forlì, (1477-1480), a master of perspective, representing in the vault, 8 windows each with an angel carrying a symbol of the Passion; below, 8 prophets and a representation of Jesus entering Jerusalem.
The Mausoleum. The Casa Santa is protected by a Marble Monument or Mausoleum, the result of the work of a number of great Renaissance artists of the time as Donato Bramante, Andrea Sansovino (1513-27), Ranieri Nerucci and Antonio da Sangallo the Young. The niches of the mausoleum contain statues of 10 Sybils, 10 Prophets and 8 low-reliefs with stories of the Life of Mary and Translation of the Holy House.
The Holy House: The original nucleus of the Holy House consists of only three walls, because at Nazareth the side where the altar now stands opened onto the entrance of a grotto. The lower sections of the three original walls consist of rows of gravel stones, a construction technique widespread in Palestine at the times of the Romans, while the upper section were added later and are made of local bricks typical of the Marche region. In the lower sections sixty graffiti have been found, similar to those of the Judeo-Christians in the Holy Land of ancient times. Above the so-called Angel's window - the window where Gabriel appeared to Mary - is placed a 13th century wooden painted Crucifix. The statue of Mary, carved in Lebanon cedarwood grown in the Vatican Gardens; the original 14th century statue was destroyed by a fire in 1921. The new statue was made by Enrico Quattrini, painted by Leopoldo Celani and finally crowned by Pope Pius XI in 1922. The statue is dressed with a dalmatian garment since the 16th century.