Katsuren Castle Ruins is a Ryukyu Kingdom-era castle site in central Okinawa, registered as a World Cultural Heritage site. From the top, reached by climbing four tiers, you look down over both the urban area of Okinawa and the sea. Park at the parking lot of the exhibition hall across the way, buy a combined ticket, and ask at the entrance for the free cart to ride up to the middle of the slope. The stone steps become slippery when it rains, so sneakers are needed.