Heybeliada, or Heybeli Ada, is the second largest of the Prince' Islands in the Sea of Marmara, near Istanbull, Turkey. It is officially a neighbourhood of the Adalar district of Istanbul. Its name, meaning 'with a saddlebag' in Turkish, in supposed reference to the valley between two hills. The island was known as Halki, Halkitis () and Demonesos (Greek: Δημόνησος) in antiquity, the first two toponyms deriving from the Greek word halkos (), meaning copper. The island was famous for its copper and copper ores in antiquity. In winter the island's population is only about 5,500, but in summer, the owners of summer houses return and the population swells to approximately 30,000. Launched in 2008, TCG Heybeliada, used by the Turkish Navy is named after the island. Until 2020, the only vehicles permitted on the island were ambulances, fire tenders, police cars etc; the only official form of transport was by horse-drawn phaeton. However, as tourism steadily increased animal-rights activists became increasingly concerned about the horses' welfare and so the phaetons were withdrawn in favour of electric vehicles. The island is served by Şehir Hatları ferries from Kabataş and Eminönü on the European side of İstanbul and Kadıköy and Bostanci on the Asian side. Geography Heybeli only covers 2.35 sqm but has four hills - Ümit Tepesi (Hope Hill, 85m/278ft), Değirmen Tepesi (Mill Hill, 136m/446ft), Köy Tepesi (Village Hill, 128m/420ft) and Baltıcıoğlu Tepes (Woodcutter's Son Hill, 98m/322ft). Attractions The island's main attractions in summer are small-scale open-air concerts and a swimming and fitness club beside the sea. The annual Independence Day march on 29 October is celebrated by the resident naval band touring the island. A large Naval High School, originally founded in 1773, overlooks the jetty. In its grounds is Kamariotissa, the only remaining Byzantine church on the island, and, more importantly, the last church to be built before the conquest of Constantinople. It is not open to the public. Also in the grounds is the grave of Edward Barton, the second English Ambassador sent to Constantinople by Elizabeth I of England, who spent his last days on Heybeli to escape an outbreak of plague raging through the city in 1598. His gravestone was later relocated to the British War Graves Cemetery in the Haydarpaşa quarter of Üsküdar. The monastery of Hagios Georgios tou Kremnou (St George on the Cliff) was founded in the late 16th century and was