The Cerchia dei Navigli was the floodable defensive moat of the medieval walls of Milan, with its southeastern part transformed into a , or navigable canal. For this reason, it was also known as the Naviglio Interno, Fossa Interna, or Cerchia Interna. Measuring 6.5 km in length and 9 m in width in its navigable section, it was completely filled in accordance with the , Milan's first urban plan, starting on 16 March 1929, with works concluding the following year. The Cerchia dei Navigli, as a whole, was a ring of water encircling the medieval historic centre of Milan, hence its name.
Description Constructed as a defensive moat starting in 1156 and transformed into a Naviglio in its southeastern part between 1387 and 1496 through canalization and expansion works commissioned by the Visconti and Sforza families, it served as the hub of the Navigli system of Milan. The only part of the Cerchia dei Navigli that remained a simple, non-navigable moat was the section towards the Sforza Castle, i.e., the northwestern stretch: its function was to supply water to the castle’s moat. The two branches of the Cerchia dei Navigli heading towards the Sforza Castle were called the Naviglio di San Gerolamo (the one descending from the southern vertex of the fortification along via Carducci) and the Naviglio Morto (the one descending from its northern vertex along via Pontaccio).
As its inflow, the Cerchia dei Navigli had the , which originated from the (i.e., the final stretch of the Naviglio Martesana, which changed its name to Naviglio di San Marco after the ), while its outflows were the Naviglio Vallone, which then flowed into the , and a spillway canal that discharged any excess flow from the Cerchia dei Navigli into the . With the filling of the Cerchia dei Navigli, the Naviglio della Martesana was entirely diverted towards the : previously, the latter was merely a spillway canal for the Martesana, as most of its flow went into the Cerchia dei Navigli. The part of the Naviglio della Martesana/Naviglio di San Marco after the Cavo Redefossi, as well as the Naviglio Vallone and the Laghetto di San Marco, were filled in concurrently with the closure works of the Cerchia dei Navigli.
The term "Cerchia dei Navigli" today refers to a , whose route largely coincides with that of the Naviglio Interno. A project is currently underway aiming to restore the ancient navigable canal (only the southeastern part of the historic Milanese canal) along the Cerchia dei Navigli road network.
History
Construction of the moat of the medieval walls in the 12th century The origins of the medieval walls of Milan date back to 1156, when the Lombard city was at war with Frederick Barbarossa. It was Guglielmo da Guintellino, a Genoese military engineer in the service of the Milanese, who designed the works and oversaw their construction.
Guglielmo da Guintellino also created their moat, possibly expanding the ancient Roman refossum, or the second moat of the Roman walls of Milan, which ran further out than the first, skirting the four castles defending Roman Milan. The innermost Roman moat ran alongside the walls.
The Milanese city walls, the republican ones to the south and west and the Maximian extension (286–305) to the north and east (although in many places the city had outgrown them due to urban expansion), were entirely made of masonry. Some significant monuments, especially churches and convents, stood outside them (the Basilica of Sant'Ambrogio, the Basilica of San Lorenzo Maggiore, the Basilica of Sant'Eufemia, the Basilica of San Babila, and the Church of San Bernardino alle Ossa, to name a few), and settlements and activities had developed around them.
The new ring of medieval walls was built, larger in scope, in 1156. It fully protected the city and channeled the waters of the Seveso and the into its moat. These waters were diverted into the new moat serving the walls, which were twenty-four arms wide; the excavated earth was then used to build large ramparts (also called "terraggi").Right next to the Pusterla di Sant'Ambrogio begins via Terraggio, which followed the course of the rampart. Their location coincides with the modern streets of the Cerchia dei Navigli road network.
This defense system was strategically well-placed but not particularly effective, as it was built with earth reinforced by palisades and defended by wooden towers. These were the materials available to Milan, far from stone quarries and lacking elevations for fortified defenses.
Frederick Barbarossa, during the , seized it and razed the city, dispersing the Milanese to nearby villages and destroying the Roman walls, the only ones made of masonry. In 1171, as a consequence of the 1162 destruction, work began on a more effective defensive system, this time in masonry, equipped with a flooded moat also fed by the waters of the Olona, which until then had been an indirect tributary of the Roman walls’ moat and underwent its second diversion in history on this occasion.
The city had long had a complex water system: it received waters from the Seveso, Acqualunga, Molia, Nirone, Pudiga, and Olona; some entered the city, some surrounded it or exited (the Nirone and the Vettabbia).
Bonvesin de la Riva describes the medieval walls of Milan in his work , written in 1288:
The medieval moat, later surpassed militarily, contributed to the city's prosperity, from trade to agriculture, as it was the regulating center of the irrigation system and the many activities made possible by flowing water: mills, fulling mills, presses, hammers, and twisting machines. Some of these activities survived even after the transformation of the ancient defensive moat into a navigable canal, which began at the end of the 14th century. The expansion work required several decades, concluding at the end of the 15th century.
Visconti-era expansion and transport of marbles for the Duomo It was Gian Galeazzo Visconti who began major works in 1387 (later continued by Filippo Maria Visconti) to make the ancient moat navigable up to the Laghetto di Santo Stefano, with the goal of transporting by water the marbles and materials essential for the Fabbrica del Duomo to build the Milan Cathedral. Until then, the only vessels navigating Milan's canals were small barges. With the decision to allow barges carrying the Duomo's marble blocks to pass, a problem arose: the draft of these vessels was much greater than that of the small barges that had navigated Milan's canals until then. For this reason, the expansion and dredging of the medieval moat were necessary.
The first works undertaken were the expansion and dredging of the medieval moat from the modern via Molino delle Armi to the Ca' Granda, where, in 1388, the Laghetto di Santo Stefano was created as the docking point for materials destined for the Duomo's construction, located 500 meters from the cathedral's construction site. After these works, the ring of water surrounding the medieval city was called the Cerchia dei Navigli.
These works made it possible to navigate from Lake Maggiore, where the quarries, used to clad the Duomo, were located, to Milan. Specifically, vessels from Lake Maggiore entered the Ticino River, then the Naviglio Grande, and finally the Laghetto di Sant'Eustorgio, from where materials were transported, with great difficulty, overland to the Cerchia dei Navigli, where they were reloaded onto barges and continued their journey by water to dock at the Laghetto di Santo Stefano.
Regarding the navigation of Milan's Navigli, the construction, between 1438 and 1439, of the Naviglio Vallone, which connected the Laghetto di Sant'Eustorgio to the Cerchia dei Navigli, and the , the first navigation lock built in Europe, was decisive. These eliminated the aforementioned overland transport of marbles from the Laghetto di Sant'Eustorgio to the Cerchia dei Navigli. The construction of the Conca di Viarenna was necessary to overcome the approximately two-meter elevation difference between the Cerchia dei Navigli and the Laghetto di Sant'Eustorgio. Vessels destined for the Duomo's construction site, unlike all others navigating Milan's Navigli, bore the inscription (Lat. , meaning "for the use of the factory," i.e., destined for the Veneranda Fabbrica del Duomo di Milano), which granted exemption from tolls. From "AUF" derives the idiom "a ufo," meaning "free" or "without paying." At one end of the Conca di Viarenna, a shrine, originally located on one of its sides, was reinstalled, bearing the 1497 ducal decree engraved on a Candoglia marble plaque that exempted vessels carrying materials for the Duomo's construction from toll and duty with the formula .
Legend has it that along the northwestern Cerchia dei Navigli, the Magna, the floating palace of Filippo Maria Visconti, the last duke of this dynasty and younger son of Gian Galeazzo, traveled. The duke moved between the castles of Milan, Abbiategrasso, Cusago,Residence of his official mistress, Agnese del Maino. and Pavia only by water, both for state affairs and to visit his many lovers (despite his frail health and a body that barely supported him). Initially, he traveled uncertain routes through ditches and canals descending to the Naviglio Grande,His movements, meticulously recorded by his biographer Pier Candido Decembrio, are known, but the exact itineraries followed are not precise. then, from 1445, through the Conca di Sant'Ambrogio, specially built in the current via Carducci (Vercellino branch of the Sforza Castle), and the Conca di Viarenna.
Connection with the Martesana in the Sforza era Ludovico il Moro, in 1496, completed the expansion and dredging of the Cerchia dei Navigli to the north,The event is commemorated by a plaque placed at via San Marco n°45 by the Municipality of Milan on its 500th anniversary. beyond the Laghetto di Santo Stefano, making it navigable also for barges carrying heavy goods; this part of the Cerchia dei Navigli extended to the Laghetto di San Marco, which was connected to the Naviglio di San Marco, the continuation of the Naviglio Martesana downstream of the , after which it changed its name. The Laghetto di San Marco, the Naviglio di San Marco, the Naviglio della Martesana, and the Conca delle Gabelle were built earlier, in 1469: with these works, the navigable Cerchia dei Navigli was completed (the innovations introduced by Leonardo da Vinci were crucial for this work). From this moment on, it was possible to navigate uninterruptedly from Lake Maggiore to Lake Como via Milan through the Naviglio della Martesana, a canal originating from the Adda River, which is itself an outflow of Lake Como.
There were also two secondary branches of the Cerchia dei Navigli, never made navigable, connected to the Sforza Castle's moat, completing the water ring around the city to the northwest: one descended from the northern vertex of the fortification via via Pontaccio, rejoining the navigable moat, while the other, the so-called "Vercellino branch" (named after Porta Vercellina, a city gate of Milan along its route), exited from its southern vertex along via Carducci, rejoining the navigable moat at its end.
The part of the Cerchia dei Navigli starting from the modern via Carducci, the so-called Vercellino branch, was also called the Naviglio di San Gerolamo, while the other branch, starting in via Pontaccio, after the filling of the castle's moat in the 17th century due to its diminished military importance, took the name Naviglio Morto, as it reached the fortification without an outlet (similarly, the Naviglio di San Gerolamo was "closed" by the subsequent filling of the castle's moat).