capital, Iwate ken (prefecture), northeastern Honshu, Japan, on the Kitakami River, southeast of the volcanic cone of Iwate Mountain. Although the largest city of the prefecture, it retains the atmosphere of the feudal period (1185–1867), when it was the Nambu fief castle town. Now primarily a commercial, railway, and cultural centre, it is known for its traditional ironware and its annual horse fairs. Pop. (2005) 300,746.