An already extraordinary trip to the secret life of the Fori Imperiali in the heart of Rome took a fascinatingly bizarre turn when we started descending the steep staircase to the basement  of the medieval Torre dei Conti, at the corner of Via Cavour and Via dei Fori Imperiali.

The 13th-century medieval tower had its fair share of an eventful life. For centuries occupying a vintage position overlooking the decaying area of the ancient forum, by the nineteenth century it had been engulfed by the dense urban tissue of the Quartieire Alessandrino, covering almost the entirety of the ancient Fori Imperiali. After Rome became the capital of the Italian Kingdom, a new avenue was carved from the railway station to the Forum, named after the Piedmontese prime minister of unification Camillo Cavour. Via Cavour expired awkwardly close to the tower and for decades urban planners debated how to connect it to the area of the Forum. Meanwhile, the first wave of serious excavations in the area, under the aegis of the archaeologist Corrado Ricci, also brought to the table the issue of connecting Piazza Venezia with the Colosseo, implicating the question of the connection with Via Cavour.

But it was under the Fascist regime that the area was transformed beyond recognition. Extensive excavations in the area of the Forum obliterated the residential quarters that had grown around and above its remains, literally paving the way for the opening of the Via dell’Impero in October 1932. Finally, Via Cavour acquired a meaningful conclusion at its junction with the avenue. Meanwhile, in 1933 a large triangular plot of land on both sides of Via Cavour – incorporating the Torre dei Conti at its westernmost tip – was earmarked for the most ambitious new project of the Fascist era in Rome – the construction of the Palazzo del Littorio. An architectural competition took place in 1934, followed by the clearing of many remaining structures in anticipation of the execution of the winning project.

Inexplicably, while the competition produced a shortlist and a second round, the location the Via dell’Impero was abandoned in favour of a new one in the Aventine quarter. The tower now stood at the tip of an incongruously empty plane. Apparently in 1934 Mussolini had formally handed it over to the Arditi, a nationalist para-military organisation that had its origins in the effervescent days of D’Annunzio’s chaotic adventure in Fiume but by the 1930s had been ‘normalised’ and integrated into the formal Fascist apparatus.

I know very little about the Arditi. Until yesterday I also knew nothing about a certain Alessandro Parisi, head of the organisation until his death in a car accident in 1938. But descending into the basement room of the tower was like entering a prohibited, eerie inner sanctum. Parisi’s body is apparently there, inside a Roman sarcophagus. An austere wooden cross covers most of one of the walls. The floor is covered with mosaics that were inspired by motifs and symbols of the Knights of St John. The room itself, dimly lit by through small openings just below the vaulted ceiling, must have incorporated remains of the old Fori Imperiali. Airless, full of unexpected shadows, dotted with the most intricate spider web formations. And somewhere there, maybe, hidden well inside the sarcophagus, the decaying body of Alessandro Parisi.

We made up all sorts of stories about the basement – about Parisi and his Arditi and their secret meetings in front of the cross and the rituals of a para-military organisation and the distorted echoes that could have filled up the room in its bizarre heyday. But Signor Parisi must have kept his secrets safe enough. I found his obituary in the Arditi newspaper – four full pages of praise for his personality and military virtue. And a photo – the only photo I could find on the internet. There is a file for him in the State Archives that I may ask to see one of these days; but I am sure that nothing in it will dispel that strange intuition that there was much, much more of Alessandro Parisi and his Arditi comrades invested in that basement hall than any document, however unguarded, could possibly betray or confirm.