Anco'na, a city of Italy on the Adriatic Sea. It was one of the chief naval stations of the Romans. At that time its citizens made a famous purple dye, used in coloring the cloaks worn by kings and emperors. On its mole stands a triumphal arch in honor of the Emperor Trajan, which is said to be the finest marble arch in the world. Ancona has a fine harbor; it is to-day the chief seaport between Venice and Brindisi. Population 63,145. The province of the same name has an area of 748 square miles, and a population of 318,683.