Miltiades Fort was an Ancient Greek fort located on the northern side of the Greek island of Mykonos during the 5th century BC. Built atop ancient ruins, and named for the Athenian general Miltiades, the fort was first infiltrated by the Spartan mercenary Kassandra in 426 BC, and she eliminated its leadership, assassinated King Kallon the Sordid, and burned its war supplies, weakening Mykonos enough for Sparta to attack and conquer the island.