Like the Buffavento and the Kantara Castles it was built so as to defend the island against the Arab raids. The castle gets its name from a saint named Hilarion. A monastery and a church were built here in the 10th century. The first references to the castle are found in the 1191 records. For some time it was of strategic importance, but later it became the summer resort of the Lusignan nobility. Especially after the invention of firearms and the increasing importance of defending the coastline it lost its functionality and importance like the Kantara and the Buffavento castles.
The castle has three parts. The parapets for the defence of the main entrance were fortified by the Byzantines in the 11th century. The lower section of the castle was being used for the soldiers and the horses. The middle section contained the royal palace, the kitchen, the church and a big cistern. At the entrance to the castle in the upper section there is a Lusignan Gate. There is a courtyard in the middle. The nobility used to live in the Eastern section, the kitchen and the other rooms for daily use were in the western section.
The panoramic view through the Queen?s window (a window carved in the Gothic style) on the second floor of the royal apartments is superb. The Prince John Tower is at the top.