Naka-gusuku is in Okinawa Island. 'Gusuku' means castle.
It was built in 15 or 16 century.
The castle walls that now remain remind me of ruins of the Inca Empire,
but maybe there's no relation between them.
It's a wonderful spectacle to look down the Pacific Ocean and East China Sea from here.

Unfortunately, in the Pacific Ocean, there's something artificial that harms the landscape. I don't know what it is.

Okinawa prefectural government is planning to restore the castle.
By the way, on the way to Naka-gusuku from Naha, you can see how huge US Futenma Airport is. It's really surprising, if we consider a size of

Rough Map of Okinawa Island