Founded and incorporated within the Castle in 1933, the Civic Photographic Archive of Milan is today one of the most important institutes of its kind in Italy. The Archive contains 850.000 original photographs datable from 1840 to the present day. The collection constitutes an important testimony of the history of photography, but also of Milanese, Italian and European arts, as well as of social and political history, exploration and travels to the near and far East.

The creation of the institute is the result of the passions and interests of the architect Luca Beltrami (1854-1933). A photographer and refined collector of photography, it was Beltrami who gave impetus to all of the city's public photographic collections.

His entire archive was left to the City of Milan, which opened it to the public in the Treasure Room of the Sforza Castle in 1936. The photographs belonging to the Beltrami collection were soon incorporated within Civic collections, which had already been archived in 1933 and included the photographic campaigns, in part carried out by Beltrami, documenting the museum artefacts and including the iconographic collection, which under the leadership of Giorgio Nicodemi (1891-1967) and Costantino Baroni (1905-1956), both directors of the Castle Museums, brought together photographs of the museums' historic and artistic heritage. The archive continued to take in important additions such as the collection belonging to art historian, collector and academic of photography (the first in Italy), Lamberto Vitali (1896-1992).