Heybeliada, second largest island in the archipelago, was known as Khalkitis or Chalki during the Byzantine period and had many copper mines, which are shut down today. There are some interesting buildings on the island such as the Naval Academy founded in 1773 and the Greek Orthodox High School. The high school is a large building up on the northern hill and in the middle of pine trees, but it's closed today. Halki Palace is a well-known hotel built in 1862 for the parents of students attending the Greek high School, it was destroyed by a fire and than restored as a hotel in 1995. A small church dedicated to the Virgin Mary stands in the courtyard of the Naval Academy. There are two small museums on Heybeliada; one is the house of Inönü, second president of the Republic, and other one is the house of Hüseyin Rahmi Gürpinar, an early Republic writer. Degirmen (Mill) is a nice picnic area on the side facing to Kasik island.
There is also a public beach set in a nice cove and a water sports club on this side of Heybeli. There are many trekking and hiking trails over the hills and through the pine groves. Several restaurants and cafeterias are lined up around the pier which gets very popular during the summer months, especially at the weekends. The island is also busy during the winter months because of many schools and the sanatorium.