SISEBOLI, a seaport-town of European Turkey, Rumelia, on the coast of the Black Sea, 80 miles N.E. of Adrianople. It has a large harbour, and a considerable trade is carried on in wine and timber. The only manufacture is the preparation of salt from the sea-water. Siseboli occupies the site of the ancient Apollonia, afterwards called Sosopolis, whence the modern name. Pop. 8000, mostly Greeks.