The project, already taken up by Bernardino Quadri, finally arrived in the hands of Guarino Guarini, the one who met the client's requests. Guarini maintained the factory he had inherited with the last intervention of the Quadri up to the cornice of the first order. From here upwards each level of the construction was designed to differ from the previous one, giving life to an articulated and harmonious geometry, formed by topped arches by concentric hexagons. He then added detailed studies of optical effects, games of light and shadows that guaranteed a fragmented view of the dome and a strong illusion in height.