On the eastern side of the New Walls, just after the Castellaccio, there is the Porta delle Chiappe (or of S. Simone).On the arch of the walls that still surround the city, the Porta di S. Bartolomeo is the last existing gate on the side of the New Walls overlooking the Bisagno and its construction was decreed together with those of S. Simone and S. Bernadino on 19th April 1632. The portal was placed at the extreme limit of a short curtain wall, between the flat bastion of St. Bartholomew and the first great pentagonal bulwark of the fortified line of the Zerbino, and was crossed by a single road that went up from the Porta dell’Acquasola, among the houses and villas of a new residential district built around the present Via Assarotti. It then continued halfway up the hillside beyond the New Walls and joined, crossing the small hamlet of Chiappazzo, with the only road heading north, running along the Bisagno stream.
Although the route was easier than that through the walls at the nearby Porta di S.Bernardino, the tunnel dug into the embankment of the walls was long and narrow and certainly rather uncomfortable.
From Codeviola’s surveys, the total length of the tunnel was about 75 palms (about 18.60 metres), its width 10 palms (2.48 metres) and its height at the arrow of the arch about 16 palms (about 4 metres). Today, the underground passage reserved for pedestrians only is 21.10 metres long and about 2.50 metres wide on the outer side (corresponding to 10 palms) and 2.25 metres wide on the opposite arch.
Next to and above part of the gallery there was a small guardhouse built on three floors, of which no trace remains today, after the 19th-century alterations, except for the walled-in compartment of a door a few steps from the entrance on the inner side of the walls. The external portal opened, without a drawbridge, onto a fenced quadrangular square of about 8 m. side and opened laterally by a gate. Today the portal is adorned with two pilasters and a simple upper entablature. On one side there is still one of the two lifting chains of the drawbridge with flat rings, made of hand-wrought iron, as well as its spherical counterweight. The bridge had the same technical characteristics as those found in the drawbridge of Fort Sperone and that of Fort S. Giuliano; constructions completed around 1830, the date of which could also be attributed to the external arrangement of the Gate.
At the beginning of this century, the gate was incorporated into the layout of Mackenzie Castle and overloaded with a mock medieval tower, an access trench, an equally mock boundary wall with merlons, embrasures, hanging arches, corbels and corbels in “neo-Gothic style”.

(Taken from “Le Fortificazioni di Genova” di Leone Carlo Forti)