In 1818, the Royal Corps of Sardinian Engineers, as part of the defence of the New Walls, decided to build a number of towers in advance of the walls themselves: four on the side of the Polcevera Valley and therefore to the west and another three on the eastern side overlooking the Bisagno Valley. The purpose of these towers was to protect the most exposed parts of the walls, and for this reason construction began at the top of the promontories that gave direct access to them.
The work began under the direction of Colonel De Andreis, based on projects that had perhaps already been presented by the previous Napoleonic government.
The towers, or what was eventually built of them, on the side facing the Polcevera, are in this order: the Torre delle Bombe (Tower of the Bombs) built under the pentagonal bastion that Brusco calls the Piana delle Bombe (Plain of the Bombs) in the context of the Tenaglia Fort, a second one in front of the Monte Moro bastion, then the present Torre di Granarolo, built to defend the homonymous gate, and finally the fourth one called Torre di Monticello along the road to Begato.
The three towers on the eastern side of the city walls are the Tower of San Bernardino, which stands under the homonymous bastion and the barely visible remains of those of Sant’Erasmo and San Simone.
The only well-preserved tower is that of San Bernardino, perhaps the only one to be completed, while the state of abandonment and degradation in which the others find themselves is also justified by the fact that they were never completed or only just begun, such as the Torre delle Bombe on the western side or that of Sant’Erasmo on the eastern side.
This was due to the conviction that the expenditure was disproportionate to the purpose, a thesis supported by Colonel De Andreis himself, convinced of the futility of these works, as Quarenghi reports in one of his manuscripts of the time.
(From “Fortifications of Genoa” by L.C. Forti )
It is situated along the trenches connecting Fort Tenaglia to Fort Crocetta and stands on an embankment in the form of a pentagonal bastion that was part of the smaller trenches designed and built by Sicre in 1747. The very simple structure of the Granara tower is related more to the primitive forms of the powder magazines and redoubts than to those of the towers built along the walls, which had their own internal structure and casing closely linked to a precise defence function. Here we are faced with two architectural volumes that are simply interpenetrating: a cylindrical enclosure wall about four metres high, which enclosed the parallelepiped, once covered by a roof, of a small grain store, as the tower was called. The inner volume, rectangular in plan and interpenetrating on the northern side with the cylindrical wall, was covered by a barrel vault, the shoulders of which can still be seen, and had an entrance perfectly aligned with that of the outer enclosure.
The geometric structuring of the two parts of the tower created two distinct environments: the internal and enclosed one of the depot and the external one, divided into two lateral spaces with circular sectors that could occasionally serve as shelter for two patrols of riflemen. The external area is thus formed by the essential continuous masonry of the cylinder, punctuated by a sequence of thin slits.