The Datça Peninsula, also known as the Reşadiye Peninsula, is an 80 km-long, narrow peninsula in southwest Turkey separating the Gulf of Gökova to the north from the Hisarönü to the south. The peninsula corresponds almost exactly to the administrative district of Datça, part of Muğla Province. The town of Datça is located at its halfway point.
Previously, the ancient Greek names for the peninsula included the Dorian or Cnidos Peninsula or the Chersonisos Cnidia.
Knidos or Cnidus (/ˈnaɪdəs/; Ancient Greek: Κνίδος, Ancient: [knídos], Modern: [ˈkniðos], Knídos) was a Greek city in ancient Caria and part of the Dorian Hexapolis, in south-western Asia Minor, modern-day Turkey. It was situated on the Datça peninsula, which forms the southern side of the Sinus Ceramicus, now known as Gulf of Gökova. By the 4th century BC, Knidos was located at the site of modern Tekir, opposite Triopion Island. But earlier, it was probably at the site of modern Datça (at the half-way point of the peninsula).
It was built partly on the mainland and partly on the Island of Triopion or Cape Krio. The debate about it being an island or cape is caused by the fact that in ancient times it was connected to the mainland by a causeway and bridge. Today the connection is formed by a narrow sandy isthmus. By means of the causeway the channel between island and mainland was formed into two harbours, of which the larger, or southern, was further enclosed by two strongly built moles that are still in good part entire.