[5] The defense of Legnano was important because its eventual conquest could have allowed the enemies of the Lordship of Milan access to Seprio via the Olona Valley, which ends at Castellanza,[6] and to the capital city itself through the use of the aforementioned road.

[2] The League's choice to place the carroccio at Legnano before the clash with Barbarossa was not fortuitous but related to the easy access to the Milanese countryside: this gateway had to be closed and defended to prevent an attack on Milan.

[2] The outline of the built-up area of early medieval Legnano was still recognizable from the map of the Catasto Teresiano, which was made in 1722, while the course of part of the walls can still be identified today by following the route of modern streets Palestro, Giulini, and Corridoni.

The Pataria was considered heretical[19] and its leader, Arialdo, had to take refuge in Legnano in the castle of the Cotta family, welcomed by Erlembaldo II: here he was singled out and betrayed by a priest who was his follower and then given into the custody of the men of Archbishop Guido da Velate.

In Landolfo Seniore's Historia Mediolanensis, an 11th-century text, it reads that Arialdo was captured:[20](LA) «[...] iuxta locum Legnani [...]»(EN)) «in the vicinity of Legnano»Subsequently, the Cotta family disappeared from the chronicles.

[21] This agglomeration of buildings is still known as the “Mensa Arcivescovile” or “Corte Arcivescovile.” The remains of the Cotta castle were found by Guido Sutermeister in 1951 during excavations for the demolition of the Humiliati convent and the church of Santa Maria del Priorato that was carried out for the construction of the INA Gallery.

Of the part of the castle that extended over the area adjacent to the present-day Palazzo Leone da Perego, no finds have come down to us due to the absence of relevant excavations at the height of the archaeological remains of medieval Legnano, which lie 1.5m below the present street level.

[1] In addition to the remains of the castle, during excavations for the construction of the INA Tunnel, the foundations of the medieval walls - with an adjoining moat fed by the Olonella River - that encircled the center of Legnano [22] were found.

It was located to the south of the town, of which it formed the southern boundary, along the modern Corso Magenta, which at the time was called Via Porta di Sotto,[11] just ahead of the entrance to Palazzo Leone da Perego and near the ancient Cotta castle.

[22] In the early Middle Ages Legnano thus appeared as a fortified citadel formed by the church of San Salvatore, the Cotta castle, which was the seat of political power, and a small group of houses gathered around the square, all enclosed by defensive walls.