Built of black lava stone, this Norman fortress stands atop a spur of rock high above the cobalt-blue sea, just outside Catania. Owing to its strategic importance, it has been a fortified strong post since Roman times, when this was the site of the Rocca Saturnia. It was conquered by Roger de Hauteville and his Normans in 1072 after his victory over the Arabs. Destroyed several times, it was rebuilt by King Tancredi in 1189. It is still possible to admire the original structure and the splendid pointed arches. The castle was later ceded to the bishops of Catania, who here in 1126 received the relics of St Agatha when they were brought back home from Constantinopolis. In 1169 there was a disastrous eruption of Mount Etna, which reached the village of Aci and the crag that emerges from the sea but which did only partial damage to the fortress at its base. The castle, from the end of the 13th cent. until the age of the viceroys, witnessed the struggles that pitted the Aragonese of Sicily against the Angevins of Naples. During the 16th cent. the castle passed through various private hands until becoming a prison under the Bourbons in 1787. Today, of the castle, one can still admire a tower, a fair part of the central body, and most importantly the dominant position over the sea. From this high point one can enjoy a fine panorama of the Faraglioni of the Cyclops and the Isle of Lachea. Inside the castle there is a little Museum with an interesting collection of minerals and archaeological items.