The city Milan, Italy, has had three different systems of defending walls. The oldest, Roman walls were developed in two stages, the first in the Republican and the second in the Imperial era. The second wall system was realized in the Middle Ages, after the destruction of the city by Frederick I Barbarossa. Finally, the latest wall system was built by the Spanish rulers. While very little remains of these walls, their structure is clearly reflected in the urbanistic layout of the city. In particular, modern Milan has two roughly circular rings of streets, namely the "Cerchia dei Navigli" and the "Cerchia dei Bastioni", which essentially correspond to the Medieval and Spanish walls, respectively. Note that a third ring of roads just beyond the Inner Ring Road, called the External Ring Road, does not owe itself to any old city walls; but was part of the 1884 Beruto Plan for the city of Milan, created and named after a municipal engineer and public servant to the local city government.
The oldest wall system was built when Milan became a Roman municipium, in 49 BC. It was essentially square, each side about 700 m long. The walls had 6 main gates, which are usually referred to as "Porta Romana", "Porta Ticinese", "Porta Vercellina", "Porta Jovia", and "Porta Cumana". Note that some of these names (for example, "Porta Romana" and "Porta Ticinese" are also used to refer to gates of later wall systems located in the same area.
In the Imperial era, while Mediolanum was capital of the Western Roman Empire, Emperor Maximian enlarged the city walls; to the east, this was intended to include the Hercules' thermae ; to the west, the new walls enclosed the arena. Overall, the new wall systems exceeded 100 hectares. Two gates where added, later referred to as "Porta Nuova" and "Porta Tonsa".
Remnants
A few sections of Milan's Roman walls are still in place, among which:
The medieval walls of Milan were built in the 12th Century, mostly as a defense against Frederick I Barbarossa, who repeatedly raided Lombardy. The perimeter of the medieval walls essentially correspond to what is now known as the "Cerchia dei Navigli", a ring of streets that enclose the historic centre of the city. The construction of the medieval defensive structure of Milan started in 1156. In the beginning, a deep moat was realized, filled up with water drawn from the Seveso and Nirone rivers. Wooden walls were added as a supplementary defensive measure, and the remnants of the Roman walls were probably exploited as well. Despite this first defensive installment, Frederick I Barbarossa razed Milan to the ground in 1162. After that, reconstruction immediately started, this time with stone walls. The final wall system was almost circular, with seven main gates and about ten "pusterle" or posterns. Most of the medieval walls were demolished between the 16th and 19th Century. The moats remained and were used as canals.
Remnants
Traits of Milan's medieval walls that still exist today include:
The so-called "Mura Spagnole" of Milan were built between 1546 and 1560 in obedience to the will of Ferrante Gonzaga, city governor during the Spanish rule of Milan. The new wall system had an overall perimeter of about 11 km, much larger than that of the medieval walls; several traits of the walls were reinforced by moats obtained by the numerous canals surrounding the city. The perimeter of the Spanish walls essentially corresponds to what is now known as the "Cerchia dei Bastioni". The walls remained well into the 19th Century, but they lost their military purpose in the mid 18th Century, being adapted as a sort of panoramic promenade by governor Gian Luca Pallavicini. Stendhal has described this promenade in his diary Rome, Naples et Florence; at the time, a passer-by would be able to see the Duomo from anywhere on the walls. From the northern part of the walls, one would be able to see both the Duomo and the Alps. The Spanish walls comprised 11 gates: Porta Romana, Porta Tosa, Porta Orientale, Porta Nuova, Porta Comasina, Porta Tenaglia, Porta Sempione, Porta Vercellina, Porta Ticinese, Porta Lodovica, and Porta Vigentina. When Milan was annexed to the Napoleonic Empire, governor Francesco Melzi d'Eril ordered the demolition of the Spanish walls and the replaced the original gates. At the time, the gates were to serve as customs duty stations, and their architecture was supposed to reflect the grandeur of the Napoleonic Empire as well as the role of Milan as the capital of the Kingdom of Italy. As a consequence, many of Milan's modern "gates" are located where the Spanish gates used to be, but only date back to the 19th Century.
Remnants
The best preserved parts of the Spanish walls are found in the surroundings of Porta Venezia, for example in Piazza Medaglie d'Oro, between Piazza Medaglie d'Oro and Piazza XXIV Maggio, and in Viale Vittorio Veneto. In Viale Monte Nero there are two small gardens obtained from the old walls.
