These ruins are what remains of a medieval castle built by knights on a Greek island in the Aegean. Where are we?

These ruins are what remains of a medieval castle built by knights on a Greek island in the Aegean. Where are we?

A Rhodes
B Halki
C Crete

The Knights of St. John built this castle in the 14th century on the island of Halki, which is closer to Turkey than mainland Greece. The castle is a popular attraction on Halki and a short uphill walk from the port village of Emporio, the island’s only town.

The correct answer is Halki.