Okinawa is the southernmost prefecture, which comprises hundreds of islands. The seas surrounding Okinawa's islands are considered among the world's most beautiful with coral reefs and abundant marine wildlife. Not only beaches, but also magnificent nature is popular destination, the ancient forests around the city offer a chance to view rare flora and fauna. For about 450 years, from the 15th to the 19th century, Okinawa prospered as the Kingdom of Ryukyu, a state independent of Japan's central government. The castles built in that era are included on the UNESCO World Heritage list.