Initially, the activity of the Cantiere marmisti (marble yard) was carried out near the monument by necessity and, until the fifteenth century, there existed a single neighbourhood extending from the area of the apse under construction to a place called “Cassina”, which housed the workers and many volunteers from all social classes involved in the construction of the cathedral.

After the closure of the lake in 1886, the workshops moved to via S. Gerolamo (now via Carducci), within the circle of the internal canals, to take advantage of the waterway that allowed for optimal transport of materials. After this stretch of the Naviglio was covered, the construction site was first moved to Viale Gorizia on the docks and finally, after water transport was abandoned in favour of road transport, to the Certosa area.

This site is equipped with state-of-the-art technology and employs highly specialised personnel, including milling and filing workers, square marble workers, ornamental marble workers, sculptors, apprentices and labourers. In the context of an increasingly vast and progressive technical evolution, the use of machine tools such as pantographs, electric drills, numerically controlled trimming and cutting machines has been introduced, which bring the pre-processing of artefacts to levels unthinkable only a few years ago, even though the artist-sculptor remains the irreplaceable element for the finishing and personalisation of the work.