- Okayama City is the capital city of Okayama Prefecture, located in the Chugoku region of Japan. It is situated on the Seto Inland Sea coast and has a population of approximately 720,000 people. Okayama City is famous for its historical landmarks and cultural attractions, including Okayama Castle, known as "Crow Castle" due to its black exterior, and Korakuen Garden, one of the three most beautiful gardens in Japan. The city is also known for being a center of education and commerce, with several universities and shopping districts. Okayama City has a mild climate, with hot summers and cool winters.