Okayama is the capital city of Okayama Prefecture in the Chūgoku region of Japan. The city was founded on June 1, 1889. As of August 2010, the city has an estimated population of 705,224 and a population density of 893 persons per km². The city is the site of Kōraku-en and the black Okayama Castle, which is ranked among the best 100 Japanese castles. The city is famous as the setting of the Japanese fable "Momotarō".