The Ursino Castle, built in the thirteenth century by order of Emperor Frederick II of Swabia on the project of the architect Riccardo da Lentini, had as purpose to defense the city and harbor. The building looks like a severe and majestic rectangular, with walls two meters thick, and four cylindrical towers a hundred feet high, with rounded corners and semi-cylindrical towers huddled in the middle of each side: only two of these towers have survived to the present day. The entrance is located in the north elevation and a niche contains a sculpture depicting an eagle catching a hare Swabian symbol of the power of the monarch Frederick IIon the town of Etna, while on the south side of the castle you can see Renaissance style windows. In 1669 an eruption modified the topography of the place where the castle which is likely to be buried: however, the lava does not diminish interest in the facilities but filled the ditch, covered the ramparts and moved a few hundred meters also coastline. Restored in 1837, it was transformed into a prison, what are testimony, hundreds of graffiti covering the walls and the jambs of doors and windows in all the rooms on the ground floor and courtyard. In 1934, the castle was again restored by the city of Catania and is currently used as a Museum, inside, private art collections, such as those of Prince Biscari or the Benedictines, and some wonderful Attic vases, terracotta archaic and a large group bronzes.