Sapporo is the largest Japanese city north of Tokyo and the largest city on Hokkaido, which is Japan's northernmost main island. It is the capital city of Hokkaido Prefecture and Ishikari Subprefecture. Sapporo lies in the southwest of Hokkaido, within the alluvial fan of the Toyohira River, which is a tributary stream of the Ishikari. Sapporo is considered the cultural, economic, and political center of Hokkaido.