Castle of the Knights of St John

The Castle of the Knights of St John commands the entrance to Kos harbour from a promontory connected to the town by a bridge over the ancient harbour moat. The Knights built it in stages from the 14th to the 16th century, creating an inner and outer circuit of walls from the proceeds of their maritime trade and piracy operations.

The interior is well preserved and open to visitors, with cannon batteries, chapels, cisterns, and storage vaults to explore. The walls give good views over the harbour and toward the Turkish coast, only 5 km away. Entry is reasonable; allow about an hour. The castle is one of the best-preserved Crusader fortifications in the Aegean.

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A story
The Knights Hospitaller built the Castle of Kos in the late 14th century using stone quarried partly from the ancient city — you can spot ancient column drums and architectural fragments built into the medieval walls. The Ottomans took the castle in 1522 after a siege lasting several months, ending the Knights' era in the Dodecanese. During the Ottoman period, Jewish refugees from Spain (expelled in 1492) were permitted to settle in Kos under Ottoman protection — their community remained on the island until the Nazi occupation in World War II.