The Castel Sant'Elmo is one of the most important examples of military architecture of the '500, is the largest in the city, is built with the characteristic Neapolitan yellow tuff and inside houses the Museum of the twentieth century with collections of contemporary art. It was built on the remains of a Norman observation tower and, because of its strategic position, whoever ruled over Naples has always tried to take possession of it. Although the first news about the Castle dates back to 1329 with Robert of Anjou, its current architecture with its 6-pointed star-shaped plan dates back to the first half of the 16th century. Over the centuries it has suffered numerous sieges, but only in the early 1970s it became a military prison, while in 1988 it was opened to the public as a museum and sometimes special events are organized. Today you can visit both the interior and the suggestive Piazza d'Armi with its panoramic terrace and the corridors inside the ramparts. From the entrance, to reach the top, a steep ramp leads to a small bridge followed by the Grotta dell'Eremita where a hermit once lived. Continuing on, you can admire the piperno portal with the coat of arms of Charles V and a guillotine gate a little further on, while on the left is the second entrance ramp. In this area you can enjoy a first enchanting view of the city through a side window, while a few meters further on you can visit the former prisons. Finally, when you arrive on the beautiful Piazza d'Armi you will cross the Torre del Castellano and you can finally walk along the corridors of the ramparts that offer a fantastic view of the city, the most complete of the old town, the sea and the islands of the Gulf.