Below the cathedral, it dates from the start of the 14C, and its white marble façade, in a more severe Gothic style than the cathedral's, was never finished. Inside, the baptismal fonts, made up of a hexagonal vessel with bronze gilded panels and a stunning marble tabernacle, were created by Jacopo della Quercia. It is quite clearly one of the great works of Tuscan sculpture produced during the transition period from Gothic to Renaissance.