Lodi is a north Italian city located in the Lombard Plain along the banks of the River Adda, 20 Km southeast of Milan. Tracing what used to be called the Castle of Porta Regale is not difficult. A cylindrical tower soars above the escarpment surrounding the old town, on the western side of the medieval city: this is the Torrione, the symbol of Lodi. From its foundation, dating back to the fifteenth century, are two massive masonry defensive walls enclosed within a moat. One of these runs south-southeast, ending with an entrance tower close to the former site of the city gate, the Porta Regale (after which the castle was named but which no longer exists). The other defensive wall stretches east-northeast along the escarpment until it reaches the Piazza Castello. Here it turns south-southeast after a sharp drop to the level of the square. Interrupted by an overhang protruding towards the city centre, the wall structure continues to the edge of the square and disappears beneath one of the adjacent streets (the Via di Porta Regale). The police headquarters (Questura) are now housed in barracks built in the eighteenth century within these walls, on the former site of the Court of the medieval castle.

While the location of the ancient fortalice is easily identified, the historical ups and downs, and the architectural layers of the castle of Porta Regale and its surroundings, are far more complex – partly because they are so closely interwoven with the origins of Lodi.

In 1158 the troops of the city-state of Milan destroyed the city of Laus (now Lodivecchio, 20 Km west of Lodi). This caused the reaction of Emperor Frederick I Barbarossa, who opposed the expansionist policy of Milan: Frederick granted the Lodigiani permission to rebuild and fortify their city, but ordered that it be moved to the western bank of the River Adda. The site chosen for this purpose was Eghezzone Hill, a high promontory overlooking the river’s alluvial valley, and surrounded on three sides by marshes (the escarpment on which the Castle stands to this very day).

Lodi was heavily conditioned by its proximity to Milan, also with regard to its fortifications and their placement. Indeed, because of its important economic, political, religious and military role, the Lombard capital polarised many forts in the surrounding area, determining their orientation: pro or contro Milan.

By the twelfth century the Porta Regale area in Lodi was deemed suitable for fortified strongholds: not only because of its location on the escarpment (higher up and more easily defendable), but also because it lies closer to Milan. At least until the fourteenth century, historical records on the fortifications in this area are limited to simple references, such as that of a castello built in 1270 by the Milanese Napo Della Torre, Senior Consul (Anziano del Popolo) and Podestà. These give way to more concrete information with the advent of a noble dynasty that dominated Lombardy between the fourteenth and fifteenth centuries: the Visconti.

In 1335 Azzone Visconti was proclaimed Lord of Lodi, which effectively brought the city into the Milanese orbit. The domains of the Visconti expanded repeatedly during the fourteenth century and military defence was thus a constant concern for the new overlords. External enemies weren’t their only problem, however: there were insurgencies to subdue; the imposition of the power of the State; the need for logistical bases, and temporary headquarters for the Court. All very good reasons for building a castle in the city. According to Renaissance historian Bernardino Corio, it was Bernabò (cousin and successor of Azzone) who ordered the construction of the current Castle of Porta Regale in 1370.

The oldest plans of the building date back to the late sixteenth century, when extensive modifications to the layout had already been made. However, they can help us identify the most likely form of the Visconti complex. At the centre of the castle area there was an irregular trapezium-shaped courtyard, open on the north-west side and surrounded by buildings on the other three. In 1784 these buildings were demolished and replaced by barracks, whose foundations in part followed the outline of the courtyard itself. The maps prior to its demolition show three sides and three towers at the corners of the inner courtyard, surrounded by the still visible curtain walls. Originally there were probably four sides with corner towers and the missing north-west section was perhaps the result of demolition or collapse after the fourteenth century (one part had collapsed in 1508). The layout of the courtyard would thus coincide with that of other castles or citadels built by the Visconti family in the same period.

It was only in the fifteenth century that the courtyard was enclosed by curtain walls. Once again, the procedure was similar to that used in other castles of the Lombard plain. Reinforced from behind by buttresses, and surmounted on the western corner by the Keep, the outer wall of the Castello di Porta Regale had a trapezoid layout and two gates: one facing the city (above the overhang of the Piazza Castello), the other looking out over the countryside to the south-west, towards the gatehouse. All the structures were built in brick since the plains around Lodi, while rich in clay, lacked suitable building stone.

The concurrent development of firearms, in particular bombards and cannons, meant that fortifications had to be made thicker and more robust. However, the changes made to the layout of the Castello di Lodi were also a consequence of the territorial losses suffered by the Visconti family during that period.

At the end of the fourteenth century, Gian Galeazzo, nephew and son-in-law of Bernabò, had managed to gain control of large swathes of northern Italy, from Ticino to Umbria, and from Piedmont to Veneto. He also managed to raise his territories to the rank of Duchy, but following his death in 1402, a serious political crisis hit the Visconti lands which risked being completely broken-up. In the first half of the fifteenth century, Filippo Maria (son of Gian Galeazzo) managed to win back some of the land, but his policies brought him into conflict with the Republic of Venice, at the time experiencing a period of marked expansion in northern Italy. The Republic came out on top, and already by 1428 the border between the two seigniories had retreated as far as the River Adda. In 1449 it stood at less than 8 Km from Lodi.

As a result, the Castello di Porta Regale was converted into a border stronghold. It is no coincidence that the fortress was of great interest to the Sforza family, who in 1450 succeeded to the Duchy of Milan. It was Duke Francesco Sforza Visconti, the son-in-law of Filippo Maria, who built the curtain walls of the castle just after the mid-fifteenth century. But their interest can also be seen in the vast collection of documents in the archives relating to the daily running of the fortress. The castle was to all effects and purposes an inhabited centre, distinct from the city and lived in by the members of the garrison. Under the command of a castellan appointed by the Duke, these soldiers had various needs, for which the castle had to provide. It was not only equipped with arms and munitions (crossbows, schiopeti, bombards, gunpowder, armours, projectiles), but also provisions, wood and clothing.

In 1535, upon the death of Francesco II, the grandson of Francesco Sforza Visconti, the territory of Milan was ceded to Emperor Charles V, and up until 1859, albeit with various interruptions, Lodi remained under the rule of the Hapsburgs: the Spanish branch until 1700, and the Austrian branch from 1706 onwards. For more than three centuries, the government of Milan continued to consider the Castello di Porta Regale as part of the fortified town of Lodi. Consequently, it kept the garrison and restored its fortifications (for example, in 1648), but from the end of the sixteenth century onwards, the use and the importance of the castle had largely diminished. In the second half of the eighteenth century, by now unsuitable for resisting assaults made with powerful cannons, the fortress was reduced to acting as simple accommodation for troops.

This use also led to dilapidation of the outer wall and keep, which contained a wide variety of architectural features, such as conduits, corridors, embrasures, latrines, passages, rooms, staircases, and wells. Between the eighteenth and nineteenth centuries, the construction of the barracks and the partial interment of the moats caused the loss of many rooms, either destroyed or bricked up. However, not everything was lost and much remains and can still be accessed today.

The entrance to the underground rooms can be found to the south of the complex, at the gate tower that adjoins the curtain wall. This structure was once part of the keep, the most important and better fortified area of the Castle since it was the area that faced towards Milan. Nowadays the keep has all but disappeared, partly due to the fact that the southern side of the Castle was hidden when a school was built in the 1940’s. Two pairs of arched entranceways, the carriage gateway and postern, open out, respectively, at the front and the rear of the gate tower and are divided by a hallway.

Inside, in the south-easterly corner, the side of a cannon embrasure has a breach that leads to a steep ramp made from earth and debris. Several metres below, it branches out in three directions: a stairway, a corridor and a breach made in another cannon embrasure. Both the latter passages lead to two adjoining rooms: one facing north, the other south.

These rooms were probably built in the fifteenth century to defend the ditch with firearms. They are similar to each other and are symmetrical: quadrangular plan, barrel vaulted ceiling and a cannon embrasure (blocked up) towards the side of the tower. To the side of each cannon embrasure a duct can be seen (also blocked) climbing the entire width of the wall at an oblique angle, whilst other openings (which have been tampered with and/or plugged up) can be found in the wall towards the front of the tower. The two rooms are connected by a passageway leading to a well that runs through the building, from the upper hallway right down to the foundations.

The stairway, however, leads to a lower level, located just below the two rooms. At the bottom of the staircase is another passageway which is similar to the first and, again, gives access to the well. To the sides are another two rooms of a similar shape and function to the previous, although slightly smaller: in actual fact, they have the ducts and the cannon embrasures (aligned with those above), while two latrines built into the front wall replace the plugged openings.

But the underground journey does not end here. The gate tower was protected on the outside by a ravelin: a small tower that stood in the ditch close to the counterscarp. Although razed to the level of today’s ring road (the Viale Dalmazia), the ravelin can still be reached from the ditch through a gap made by a breach in a cannon embrasure. The ancient use of firearms is once more apparent, as is the modular development of the structures: two adjoining and communicating rooms (northsouth alignment, but with no well), barrel vaulted ceiling, quadrangular plan, cannon embrasure, side ducts and windows cut into the walls facing towards the gate tower.

But there is more. A corridor leads away from the southern room, covered by a vaulted ceiling and created behind the counterscarp of the old ditch (now hidden by the road above the Via Acquedotto). This corridor leads out into another room which, in turn, opens out towards the north-east though a gap: perhaps another breach in a cannon embrasure, where the counterscarp can be crossed to reach another passageway. Here one side of the vaulted ceiling rests on the actual counterscarp, the other side on brickwork built in the nineteenth century when the ditch was filled in. The passageway eventually ends at the base of what was once the Porta Regale: its foundations still exist today and are used to support a small building that overlooks the Via Acquedotto.

The southern room of the ravelin also has an entrance that is above floor level and which opens in the wall opposite the castle. It enters the low, narrow stairwell with a ramp leading upwards in a south-southeasterly direction only to come to an abrupt halt against a fairly recent infill.

Instead, another corridor branches off from the north room, symmetrical to the one that reaches the Porta Regale. However, if you follow the counterscarp for a few metres, it is interrupted, almost totally blocked by earth and debris. Only the upper part shows that it continues onwards.

From this point on the passsageway can no longer be followed and the counterscarp itself is interrupted at the height of the Torrione, since the entire north section was destroyed in the 1990’s to make place for a parking lot. At that time the adjacent corridors were also lost, as can be witnessed from photographs that were taken during the work. Said work also damaged the castle foundations towards the Piazza Castello, where the junction with the city walls once was.

Notwithstanding the demolitions that took place over decades, research brought to light underground constructions that extend even beyond the Castello di Porta Regale. Departing from the Piazza Castello a number of walled structures crisscross underground towards the Piazza Vittoria. This direction is significant since this is where the Broletto and the Cathedral are located: the political and religious heart of Lodi. Not only that. These structures lead to several other locales within the old city: they continue under the streets in the direction of the Adda; they go around the centre, following the path of the ancient walls; they split and branch out under buildings, churches and convents.

Many of the passageways are still there and accessible. Some of them have been incorporated into the basements of dwellings while still others have been identified thanks to georadar tracings. In 2007, for example, by sounding beneath the Piazza Vittoria and surrounding area, spacious underground rooms were discovered but their purpose still remains unclear.

There are indeed many opportunities for research and investigation since these passageways involve an entire city: a Lodi that is not visible on the surface but which nonetheless exists just a few metres below the city streets. It is an area for further research, the key to which can be found underground, branching out from the Castello di Porta Regale to the winding paths of the city centre. For each of the walkways, rooms, stairwells and branches there is an opportunity for historical research. This is the underground history of Lodi: unusual, unknown and just waiting to be explored.