Frenchman, Nicolas de Bonaventure, was appointed chief engineer. He added Rayonnant Gothic element, a French style not typical for Italy. He decided that the brick structure should be panelled with marble. The Fabbrica del Duomo was granted exclusive use of the marble from the Candoglia quarry and exempted it from taxes.
During the centuries of construction, grand Gothic and Roman Renaissance designs were planned for the Duomo, most of which were never completed, but these designs, particularly those of Carlo Buzzi, became inspiration for the later completion of the cathedral façade.
Interestingly, over the centuries, those who wished to donate privately to the Duomo upkeep and restoration are recognized with small plaques (many with no names, just dates) located in the stonework of the rooftop buttresses.
The Madonnina Spire or guglia del tiburio ("lantern spire"), is one of the main features of the cathedral, and was erected in 1762 at the height of 108.5 m (356 ft). The spire was designed by Francesco Croce. At the top of the spire is the polychrome Madonna statue, designed and built by Giuseppe Perego in 1774. Our guide asked us to imagine travelers over two centuries ago, after weeks of crossing the Italian countryside, approaching the city and seeing the sparkling gold Madonnina high up in the horizon. The Madonna would be seen as reassuring to pilgrims and traders that they would soon be in the city of Milan.