 A large round tower stands outside the castle walls to the southeast.Underwater archaeologists have discovered what appears to be a 2500-year-old harbor associated with the origins of the first Greek settlement of Paleopolis (which preceded the ancient city of Neapolis, now Naples) in the sea next to the castle.Four tunnels, a 10-foot-wide street demonstrating furrows consistent with cart traffic, and a trench which was likely built as a defensive structure for soldiers were discovered submerged immediately adjacent to the castle.