The Duomo di San Martino is Lucca's cathedral, a complex Romanesque building whose construction began in the 11th century and continued for several hundred years. The famous asymmetrical façade — three-bayed in most of its arcading but squeezed by the pre-existing bell tower on one side — is one of the great curiosities of Italian medieval architecture. Inside, the cathedral holds Jacopo della Quercia's tomb of Ilaria del Carretto (1406), one of the most beautiful sculptural works of the early Renaissance, and the Volto Santo, a dark-wood crucifix of Byzantine origin venerated since the 8th century.
The Volto Santo (Sacred Face) is the spiritual heart of Lucca. Legend says it was carved from life by Nicodemus and miraculously transported from the Holy Land to Lucca. Whatever its origins, it has been the object of intense local devotion for over a thousand years, and a procession in its honour — the Luminara di Santa Croce — takes place every September 13th.