The origins of the massive Angevin- Aragonese Castle are uncertain: most likely it was built in the 6th century, in the course of the Gothic War, or during the 7th century to defend the town from the Lombards’ advance. First documents mentioning it date to the age of Frederick II of Hohenstaufen, who strengthened it in 1233. The current structure is made of two different buildings: the “Angevine” one, in the lower sector, dating to the House of Anjou’s rule in the Kingdom of Naples; and the “Aragonese”, at the top, built by Emperor Charles V, together with the other fortifications that made Gaeta one of the strongest fortresses in southern Italy. The Angevine wing housed a military jail until the 1980s (German war criminal officers Walter Reder and Herbert Kappler were imprisoned here). Now it is a property of the Gaeta municipality, which uses it for conferences and exhibitions. In the dome of the tallest tower is the Royal Chapel, built by King Ferdinand II of the Two Sicilies in 1849.