Kastri is a small rocky islet located just off the coast of Kefalos in Kos, Greece, and is one of the most recognizable landmarks in the area. The islet is particularly famous for the charming white and blue chapel of Agios Nikolaos (Saint Nicholas), which sits on its hilltop. The chapel is dedicated to the patron saint of sailors, making it a symbol of protection for local fishermen and seafarers.

Accessible by boat or by swimming across the shallow waters, Kastri provides visitors with stunning views of the surrounding bay and Kefalos village. The clear, turquoise waters around the islet are ideal for snorkeling and swimming. The church, with its simple, iconic design, is a favorite spot for both tourists and locals, especially for weddings and religious celebrations.

Kastri and its Agios Nikolaos chapel create a postcard-perfect image, with the backdrop of the blue Aegean Sea and the ancient ruins of Kefalos nearby, making it a must-see attraction for those exploring Kos.