In the 12th century, while on pilgrimage to the Holy Land, William of Vercelli stopped here, on the southern slope of Mount Virgin, not far from Avellino, to build a sanctuary dedicated to Our Lady and found the Virginian monastic order. From that time, the basilica and monastery experienced a period of great splendour thanks to the favour of the kings of Sicily. They then underwent a period of decline until becoming a commendam in 1430. The basilica, divided into two parts, is accessed through a courtyard. Opposite is the entrance to theAbbey Museum, which houses a 12th-century abbot's chair with Arabic-style inlays, the late 12th-century panel of the Madonna of St. William and a 13th-century wooden crucifix by the French school. There are also paintings from between the 15th and the 18th centuries, statues from the 12th-15th centuries and vestments from the 12th-13th centuries. The Permanent Nativity Exhibition displays a Neapolitan nativity scene and examples from around the world from the 17th century to the present day. To the left is the Old Church, a Baroque reconstruction of an earlier Gothic building; the high altar, inlaid with mother-of-pearl, lapis lazuli and agate, dates back to the mid-17th century, while in the Blessed Sacrament Chapel, to the right of the main chapel, there is a canopy from the second half of the 13th century (later modified), with a 15th-century marble tabernacle. To the left of the old church, an archway gives access to the new church, built in 1952-61 inspired by Romanesque forms. Built on a Baroque place of worship, of which it incorporates almost the entire left aisle, it is imposing (measuring 54 m long by 25 m wide). What catches the eye, however, is the high altar, on which – above a throne of marble, bas-reliefs and bronze and silver statues – is proudly displayed a large painting of the Madonna of Montevergine, known to the faithful as 'Mamma Schiavona', a work of art from the end of the 13th century by Montano di Arezzo, venerated every year by more than a million pilgrims who come here. A modern monochrome mosaic by Jànos Hajnal serves as a backdrop for it. The crypt houses the tomb of William of Vercelli.