The Martesana Canal, or Naviglio Piccolo, was built owing to the initiative of Francesco Sforza. The works on its construction began in 1475 and finished in 1496, under the guidance of Ludovico il Moro. This artificially channeled watercourse originates from the Adda river, under the castle of Trezzo, and arrives in Milan passing by the Cassina de ‘Pomm, near the flanked eponymous garden, and it ends its run (buried) in San Marco. Of a total length of 38 km this waterway irrigates, with its over 129 outlets, nearly 25,000 hectares of crops alongside the Via Padana Superiore (SS 11), the ancient Roman road that ran near the Adda.
The pond of Via San Marco, as well as most of the inner dich, was placed underground in the 20s of the twentieth century, but when it was in use it worked as a real port in Milan. Originally, the Martesana Canal was also designed with the aim to provide power for the mills, the grinders, the oil presses, the spinning wheels and the paper mills in the area, but also to allow Milan to have a navigable canal to easily reach the Valle dell’Adda and Bergamo.
It should be remembered that, before it was buried, the canal ended in the pond of San Marco, which branched off along Via Pontaccio ending its run in the moat of the Castello Sforzesco (hence the name ‘dead canal’), and on the other side through the Tombone San Marco (called Tombum di San Marc) it flowed in the inner ditch under the ramparts of Porta Nuova, to reach the Darsena of Porta Ticinese. Further up, two basins emptied the waters of the Naviglio Martesana into the Naviglio Interno, the waterway that ran all around the historical center of Milan.