Heybeliada Island (also spelled Heybeli Ada) is one of the Princes' Islands in the Sea of Marmara, near Istanbul, Turkey. It is the second-largest of the islands and is known for its beautiful natural surroundings and its quiet, laid-back atmosphere. Heybeliada Island is accessible by ferry from Istanbul, and it is a popular destination for swimming, sunbathing, and picnicking. The island is also home to several historic landmarks, including the Ayios Dimitrios Church and the Halki Seminary. Heybeliada Island is a popular place to escape the hustle and bustle of the city and enjoy the beauty of the Turkish countryside.