The marble the Duomo is made of comes from here.
The living springs of Milan cathedral lie above the hamlet of Candoglia, in the municipality of Mergozzo, on the left of the river Toce at the entrance of the Ossola valley, in Piedmont.
Its crystalline beauty streaked with rose, combined with great resistance due to its exceptional physical and chemical characteristics, brought an extraordinarily valuable contribution to the construction of the church and conditioned its architecture, statics and ornament.
It was Gian Galeazzo Visconti who decided to replace brick, which had originally been chosen for the construction of the Duomo in its initial plan, with marble. To this end, on 24 October 1387 he ceded the Candoglia quarry to the Veneranda Fabbrica and granted free transport of the marble to Milan via the waterways. The material was transported to the city from the river Toce to Lake Maggiore, along the Ticino river and the Naviglio Grande canal and then inside the city to the Sant’Eustorgio docks. Through a system of locks built by the Fabbrica it reached a small lake (laghetto, in Italian, now a street named via Laghetto) a few hundred metres from the Cathedral’s construction site, in the heart of the city.
Even after the lake was closed, the transport of marble blocks to Milan continued to be done along the waterways until 1920, after which the marble was carried on roads.
The small width of the vein of this particular marble makes it difficult and expensive to extract. This uncertainty, however, has never curbed the enthusiasm of the Veneranda Fabbrica, which still faces the great enterprise of preserving the monument with responsibility, taking care of the maintenance of the quarry through the use of highly qualified personnel and with the support of modern technology.