These are remnants of a larger defensive structure that once included five towers and walls that entirely enclosed a ducal palace and supporting town.
The castle town could hold more than a thousand defenders and had been for centuries one of the most efficient and impregnable fortresses of central Italy, reputedly withstanding a siege of seven years.
It could not, however, resist the gunpowder artillery that Charles VIII of France used during his conquest of Naples in 1494-1495.
Monte San Giovanni, then a border fort of Naples, fell after eight hours of bombardment.
The rest of Naples put up little resistance after seeing the result at Monte San Giovanni.