Castello di Gaeta, Medieval castle in Gaeta, Italy

Castello di Gaeta is a medieval fortress built on raised terrain overlooking the Tyrrhenian Sea, featuring thick stone walls and defensive towers arranged for maximum protection. The structure occupies the hilltop with interconnected fortified areas that once housed garrison troops and supplies.

The site was probably first fortified in the 6th century during the Gothic War, or in the 7th century against Lombard expansion, when Gaeta appears in documents as "Kastrum". Frederick II of Swabia stayed in Gaeta during his struggles with the papacy and had the castle fortified in 1223. The present complex of about 14,100 m² consists of a lower Angevin building and an upper Aragonese one; Charles V later strengthened the whole fortress.

The Cappella Reale, commissioned by King Ferdinand II of Bourbon in 1849, occupies the dome of the Torre di Gaeta, the tallest tower of the Aragonese wing. The Angevin wing held Gaeta's military prison until 1980, where inmates included Nazi war criminals Herbert Kappler and Walter Reder and Italian Jehovah's Witnesses jailed for refusing military service.

The castle is open to visitors only in guided groups, so plan around a scheduled tour rather than a free walk-through. The two wings are still in institutional use: the Angevin wing belongs to the University of Cassino, the Aragonese wing houses the Guardia di Finanza naval school, so access is limited to the visiting route.

The Angevin wing held Gaeta's military prison until 1980; its inmates included the Nazi war criminals Herbert Kappler and Walter Reder, and Italian Jehovah's Witnesses jailed for refusing military service. The wing was then handed to the University of Cassino.