On the western side of northern Andros, on a high and steep rocky peninsula, is the castle of Ostodosia or Makrotantalos, which, from its strategic location, controlled the Kafirea Strait. Today, the ruined enceinte wall and two towers survive, the largest of which rears up in the middle of the enclosure. It is a rectangular building, the ground floor of which served as a rain-water cistern. In shape and structure, the castle of Makrotantalos is most like to the fortress of Kato Kastro, but on a smaller scale. It was connected to the mainland by a single-arched stone bridge, of which the bases of the arch can be still made out.
