This artifact, made up of over 500 pieces of interlocking wood of various essences, constitutes one of the largest and most important wooden models in the history of architecture, that is the three-dimensional project that was to show the building that was being built, thus helping the construction site workers during construction.

Testimony of a project developed starting from the last decade of the fifteenth century, with the contribution of great architects, from Bramante to Leonardo, it is a masterpiece of carpentry, carved in every external and internal detail.

This wooden model illustrates the project conceived by the Marquis Luigi Malaspina di Sannazzaro, who in 1809 was elected head of the Fabbriceria della Cattedrale, together with the Milanese architect Carlo Amati. Starting from what had already been built up to that moment (the apsidal part and the central octagon pillars), the model shows their idea of continuing the construction, which included a Greek cross building with a lower dome and a facade from classical temple, with eight Corinthian columns supporting a triangular pediment. The project was not, however, implemented, because in 1838, when the construction site was restarted, it was decided to return to the longitudinal project, transmitted by   large Renaissance wooden model.