NICOMEDIA, in Ancient Geography, a metropolis Nicomedia of Bithynia, built by Nicomedes the grandfather of Prusias. It is situated on a point of the Simus Atlacenus, (Pliny); furnished the Beautiful, (Athenæus): the largest city of Bithynia, (Paulianus), who says it was formerly called Atlacum; though Pliny distinguishes Atlacum and Nicomedia as different cities. Nicomedia was very famous, not only under its own kings, but under the Romans: it was the royal residence of Diocletian, and of Constantine while Constantinople was building, if we may credit Nicephorus. It is still called Nicomedia, at the bottom of a bay of the Propontis in the Hither Asia. E. Long. 30. o. N. Lat. 41. 20. It is a place of consequence; carries on a trade in silk, cotton, glass, and earthen ware, and is the see of a Greek archbishop.