From Forte Begato, descending along the walls and the ramparts of Garbo, one reaches the Granarolo gateway that from the homonymous climb leads in the direction of Piani di Fregoso and, through the Garbo climb, to Val Polcevera. Along the road of Piani di Fregoso you can see the ruins of two round towers, the one called Granarolo, just under the homonymous door and the one of Monticello. Both of them face the salients of as many bastions as seen in the eastern sector.
On the slopes facing the old city we can still recognize several powder magazines, the largest of which flanks the road always near the door. Before reaching the Tenaglia you can see outside the walls the ruins of two other round towers more easily reachable from the Crocetta fort, as indicated below.
To access Tenaglia, leave the main roadway at the point where Via Bartolomeo Bianco passes tangent to the walls. Then along an abandoned track, you add and pass the walls on a sortie that ends in front of the drawbridge entrance to the fort. The construction, located on a natural promontory (217 meters above sea level) which gave its name to the oldest fortress, faces the whole lower Polcevera valley and the crags of Coronata, bordering to the east with the area of the Castagna cemetery. On the extreme position of the flat ridge, in the 16th century, the famous “Bastia di Promontorio” was built, which together with the Bastia di Peralto and the Castellaccio dominated the whole city from above. This fortification which included two towers and a rectangular walled enclosure with four bastions, as can be deduced from the views of the city in the sixteenth and seventeenth centuries, was completely flattened during the construction of the New Walls.
On the Piano delle Bombe was then built the characteristic horn-shaped Tenaglia. Throughout the eighteenth century were performed partial works of modification, but only between 1815 and 1836, by the Sardinian Military Engineers, the fortification reached the autonomous physiognomy that the work of closing in a single enclosure of the early century had failed to give it. Used as an anti-aircraft battery during the last war, it was hit repeatedly, causing considerable damage especially in the sea front. In the corner of the connection between the tong and this part there is a powder magazine with access from the top of the square.
(Taken from “I forti di Genova” Sagep Editrice)