It has an area of 21 hectares, and is about four times as long as it is broad.
In pre-Turkish times, the island was called Daphnusia (Δαφνουσία), Apollonia (Ἀπολλωνία), and Thynias (Θυνίας). The last of these names is derived from the Thynii, a people of Thracian origin, who occupied all the coast of Bithynia. It is mentioned by the geographer Ptolemy (5.14.1) and Pliny the Elder (5.32), and by Strabo, and also in the Periplus of the Euxine Sea. The names Thynias and Daphnusia are both given by Ptolemy, Thynias by Pliny and Strabo.
Although the settlement on the island never attained the rank of "city", it became, at a relatively late stage, a bishopric. This was at a relatively late stage, for there is no mention of it in the Synecdemus. The first of the Notitiae Episcopatuum in which it appears, always under the name "Daphnusia", is the early 10th-century one attributed to Byzantine Emperor Leo VI the Wise. The Greek Orthodox Church venerates as a martyr bishop of Daphnusia a certain Sabas, of whom nothing else is known, while extant documents show that Leo took part in the Council of Constantinople (869), where he expressed repentance for having deserted Ignatius of Constantinople in favour of Photius, and that his successor Antonius was at the Council of Constantinople (879), which reinstated Photius. No longer a residential bishopric, Daphnusia is today listed by the Catholic Church as a titular see.
Long breakwaters extend out from the island, forming a safe harbour for ships.
- [http://www.ns1.newadvent.org/cathen/14714a.htm Siméon Vailhé, "Thynias" in Catholic Encyclopedia (New York 1915)
- "Η νήσος Δαφνουσία". Εγκυκλοπαίδεια Μείζονος Ελληνισμού: Μικρά Ασία. Foundation of the Hellenic World. Retrieved 2014-01-10.
- Michel Lequien, Oriens christianus in quatuor Patriarchatus digestus, Paris 1740, Vol. I, coll. 629-630
- Ἀρριανοῦ Περίπλους Εὐξείνου Πόντου, 18
- Raymond Janin, v. "Daphnousia" in Dictionnaire d'Histoire et de Géographie ecclésiastiques, vol. XIV, 1960, col. 82
- Annuario Pontificio 2013 (Libreria Editrice Vaticana 2013 ISBN 978-88-209-9070-1), p. 878
- Kefken Adası Lighthouse
- Kefkenada (Kefken Island) Light
- Sergei R. Grinevetsky, Igor S. Zonn, Sergei S. Zhiltsov, Aleksey N. Kosarev, Andrey G. Kostianoy (editors), The Black Sea Encyclopedia (Springer 2014 ISBN 978-3-64255227-4), p. 403
- "Kısaca Kefken Adası" (in Turkish). kefken.com. 2006. Retrieved 2015-01-10.