NICOMEDIA, a town at the head of the Sinus Astacenus, which opens on the Propontis, was built in 264 n.c. by Nicomedes I., king of Bithynia, and has ever since been one of the chief towns in this part of Asia Minor. It still retains the ancient name under the form Ismid, and it is the terminus of a short railway. Its situation made it a convenient centre of government. It was the metropolis of Bithynia under the Roman empire (see NmEA); Diocletian made it the capital of the East, and fixed his court there. It retained its importance even after Constantinople was founded, for the roads from all parts of Asia Minor to the capital converge at Nicomedia.