The following is according to the unesco website:
Established in the 9th century as Benedictine abbey, the church became famous in the mid-11th century when the belief spread that it held the relics of St. Mary Magdalene. It became a place of pilgrimage as it was located on one of the roads leading to Santiago de Compostela. The church of St. Mary Magdalene is a masterpiece of Burgundian Romanesque art as exemplifed by its architecture, capitals and carved portal. But it is the sculpted portal between the nave and the narthex which has brought universal fame to Vézelay. It is a major monument of Western Romanesque art.