St Nicholas Monastery, or Aya Nikola Manastırı, is the sight that lifts Kıyıköy above an ordinary seaside village. It was cut into the rock near the Pabuçdere, with spaces for a chapel, monks' cells, storage rooms, and a holy spring.
The monastery is weathered and partly battered by history, including the population exchanges that emptied the Greek Orthodox community after 1923. Go for the roughness as much as the architecture: it feels half ruin, half cave.