Khalkidhikí (khälkēħēkēˈ) [key] or Chalcidice kălsĭdˈĭsē, peninsula (1991 pop. 92,117), NE Greece, projecting into the Aegean Sea from SE Macedonia. Its southern extremity terminates in three peninsulas: Kassandra (anc. Gr. Pallene ) in the west, Sithonia in the center, and Athos in the east. The region is largely mountainous, dry, and agricultural. Olive oil, wine, wheat, and tobacco are produced; magnesite is mined. In antiquity the peninsula was famous for its timber. Olynthus and Potidaea were the chief towns in antiquity; Poliyiros is today the leading town and an administrative center. The peninsula was named for Khalkís, which established colonies there in the 8th and 7th cent. B.C. In the 4th cent. B.C. the peninsula was conquered by Philip II of Macedon, and in the 2d cent. B.C. by Rome. The subsequent history of Khalkidhikí is essentially that of Thessaloníki.