The Ara di Ierone II is the enormous rock-cut base of an altar built for King Hieron II in the 3rd century BCE. At nearly 200 metres long, it was one of the largest altars of the ancient Greek world, used for major public sacrifices in the city that once rivalled Athens in wealth and ambition.
Most of the superstructure has gone, so the appeal is scale rather than decoration. It makes most sense as part of the Neapolis Archaeological Park, combined with the Greek Theatre, the Roman Amphitheatre, and the Ear of Dionysius.