The first fortress was built in 474 BC by the Greek-Syracusan, Gerone I, who had arrived to help the Cumaeans in the war against the Tyrrhenians. Amongst other buildings, tall towers were erected so as to observe the movement of enemy ships. When the war was over Gerone maintained possession of the island, which was later occupied by the Parthenopeans.
In 326 BC the island was conquered by the Romans and then again by the Parthenopeans. The plundering and the many long periods of domination by the Visigoths, the Vandals, the Ostrogoths, the Arabs, the Normans, the Swabians, and the Angevins completely transformed Gerone's fortress.
In 1301 the last eruption of Mount Epomeo destroyed the city of Geronda, which used to be where the pine forest now grows: and the people took refuge on the small island. In 1441 Alphonso ofAragon rebuilt the old Angevin Castle, he joined the tiny island to the larger one by building an artificial bridge and constructed strong walls and fortifications. Inside these walls, nearly all the inhabitants of Ischia found refuge, and also protection from incursions by pirates.
Towards the beginning of the 18th century the fortress gave hospitality to 1892 families and also to the Convent of the Clarisse, the Abbey of the Greek Basiliani, the Bishop, the Chapter and the seminary, and also to the prince with his garrison. There were 13 churches and of these 7 were parishes. In about 1750, when the danger from pirates was over, people started to look for more comfortable living accommodation in the various Municipalities of the island of Ischia.
In 1809 the English besieged the island, at the time under French rule, and shelled it until it was nearly totally destroyed. In 1823 the King of Naples got rid of the remaining 30 inhabitants and reduced the Castle to a place of detention. In 1851 the King reserved the Castle as a political prison and later still it became a place of confinement.