The coastline of Astypalaia is rugged, featuring coves and beaches. A narrow strip of land, around 100 metres wide, known as Steno, divides the island into two sections: the inner and outer island. In the southeast, there are several small islets, such as Agia Kyriaki, Chondros, Kounoupi, and Koutsomyti.
To the west lie the islets Ofidousa, Htenia, Pontikousa, and others. The capital and main port of the island is Astropalia, also known as Chora.
The eastern part of Astypalaia, the surrounding islets, Ofidousa, and their marine zones (Cape Landra – Cape Vrysi) are designated as protected habitats , covering a total area of 70.32 square kilometres. This recognition ensures the preservation of the area’s unique biodiversity and ecosystems.