Okinawa has a rich history dating back to the Ryukyu dynasty. Across the island you will find many castle ruins that were destroyed in WW2 in the famous battle of Okinawa. Shuri is the only castle that has been completely restored to its magnificent former glory. You could spend a whole morning meandering around the beautiful site and surrounding shrines.
It has been listed as a UNESCO World Heritage site and well worth a trip down south to the bustling Okinawan capital of Naha.