The Bolognese architect, collector and historian Carlo Bianconi, secretary of the Brera Academy since 1778 and author of a famous guide to Milan published in 1783, collected about four hundred original architectural drawings and some engravings of Milanese buildings in ten large-format volumes datable between the fourteenth and eighteenth centuries. In tome II in particular, he ordered the documents relating to the design history of the Duomo. This very important collection, now preserved in the Civic Historical Archives and Trivulziana Library, became part of the civic collections thanks to the purchase carried out by the Municipality of Milan from Antonio Vallardi in 1872. It still constitutes a precious testimony today both for the wealth of graphic documentation contained both for the original prefaces that Carlo Bianconi inserted in the body of the volumes, giving significant evidence of erudition and critical acumen.

This work, belonging to the permanent collection, is open to the public for conservation reasons only on the occasion of temporary exhibitions.