The marble "Virgin with Child", in the lunette of the central Door of St. Petronio is the work of a Sienese artist, Jacopo della Quercia. Following the Renaissance pattern for adorning the town, the artists were called frorn other regions: architects and masons from Lombardy, Venice and Tuscany; sculptors especially from Tuscany; painters and miniaturists from Ferrara and Modena. As far as sculptors were concerned, there were no local artist of outstanding importance, also because the requested material, marble, was not to be found in the Bologna area. As a consequence, terracotta was used, but, again by 'foreign" artists.  As earIy as the 13thCentury in the church of St. Domenico, some Tuscan artists, Nicola Pisano, Arnolfo di Cambio, Lapo and Fra Guglielmo had sculptured the ark of St. Domenico on which the cymatium was later added by Nicolo, who, from this work got his nick-name "dell'Arca"; in the 16th Century later on this ark was also adomed with a S. Procolo, a St. Petronio and an Angel sculptured by Michelangelo. And it was again Nicolo dell'Arca from Puglia who, in the 15th Century, made the "Virgin with Child" in terracotta for the facade of the Municipal Palace and the great "Mourning the Dead Christ", again in terracotta, for the church of St. Maria della Vita (above).

Bolognese architecture and town-planning got their original character from brickwork. Both selenite which still adorns the base of some towers (the Altabella Tower, for example), and sandstone, warm and porous but as friable as sand, are typical materials of the area in which stems the geological phenomenon of "calanchi" particular to the Bolognese hills. In the 15th Century the facade of the Spirito Santo Oratory in via Val d'Aposa was also made of brick. The colour of the town, resulting from these materials was later emphasised, when buildings were rendered in brick-red, ochreyellow and beige; this habit was to become a rule, laid down by the Church for religious buildings. The domes too, covered in copper-leaf, were red and would later turn into green-grey because of the rain.