Most İstanbullus refer to the Princes' Islands as 'The Islands' (Adalar). Lying 20km southeast of the city in the Sea of Marmara, the islands are a popular destination for a day escape from the city but are oppressively crowded between May and October, when visitors can number up to 50,000 per day on weekends. Five of the nine islands in the group are populated; most visitors head to the two largest, Büyükada and Heybeliada.
The islands have been populated since the 4th century BC, acquiring their present name in the 6th century AD after coming into the possession of the Byzantine prince, Justin. The first Greek Orthodox monastery was established in 846 and regular ferry services from İstanbul began in 1846. Wealthy İstanbullus then began to purchase holiday villas here. Büyükada and Burgaza were popular with families of Greek and Jewish heritage; Heybeliada was predominantly Greek.