The city is a planned city in Japan. The world's fair (Expo '85) was held there in 1985. A full size rocket in the city park still reminds of this event.
As of 2003, the city has an estimated population of 195,686 and the density of 688.87 persons per km². The total area is 284.07 km².
The city was founded on November 30, 1987.