The oldest part of Mykonos Town, built on a low hill above the harbour on the site of the medieval Venetian castle. The neighbourhood is a tight maze of whitewashed lanes, with houses packed closely to deny pirates a straight line of attack — the defensive logic that shaped the layout of Cycladic towns across the islands. Paraportiani Church sits at the foot of the hill; the Folklore Museum occupies a captains' house near the top.
Kastro is quieter than the central Chora streets, especially in the early morning and evening. The views from the upper lanes take in the harbour, the windmills, and on clear days the silhouette of Delos. The district has fewer restaurants and shops than the rest of town, which is part of its appeal.