Pontikokastro is one of the most enigmatic monuments of the island. It is located on the hill of Noulia, at the eastern end of the series of windmills that dominate the settlement and the port. The regural masonry of its round platform recalls regular tholos tombs. To date, no reliable interpretation exists regarding the function of this building. By some scholars it has been linked to the Trophy set up on the island by the Lacedaemonians for their victory in a naval battle against the Athenians during the Peloponnesian War (412/411 BC); others have dated it to Mycenaean times. According to reports, the monument was pillaged more than once and valuable information about its use has thus been lost.
