Kizil Adalar (kəzŭlˈ ädälärˈ) [key] or Princes Islands, group of nine small islands (1990 pop. 19,413), c.4 sq mi (10.4 sq km), NW Turkey, in the Sea of Marmara, near İstanbul. The islands are a popular resort area. They were used as places of exile in Byzantine times. There are several old monasteries and churches. Büyük Island is the largest of the group.