In the south-east of the island, the Site of Izena Castle tower over a backdrop of picturesque coastline. To the back-right is Urugami Island, where the gods are said to have alighted during the creation of heaven and earth, while Iheya Island - the birthplace of Samekawa Ufunushi - can be seen in the top section. Izena Castle Site was part of a pyramid-like rocky mountain, and displays a truly impregnable appearance. Indeed, it is said to have actually withstood an attack by the Hokuzan Kingdom. It is considered to have been built during the 13th~14th centuries, which means some 100~200 years before Sho En was born.

The first lord of the castle was Samekawa Ufunushi, who was from Iheya Island, and also the grandfather of Sho Hashi, who unified Ryukyu. Even in that sense, the castle has an important position in the history of the Ryukyu Kingdom, and currently it is designated a Cultural Property of Okinawa Prefecture. While it is covered in boulders of Ryukyu limestone and deep greenery, parts of the stone wall remain as a vivid reminder of the time when it functioned as a royal castle.

There are many cultural properties that give hints of the eternal history even earlier than the building of Izena Castle. Included among them are the human bones from roughly 3,000 years ago that were unearthed on Gushikawa Island, which floats in the sea to Izena Island's north. The arms were decorated with bracelets made from sea shells, from which it can be understood that people living there had a high standard of living during the times that were still described as the Jomon Period in Japan.

On Izena, shell mounds have been found all over the island. They indicate that people were leading lives there in prehistoric times some 2,500 to 3,000 years ago, and in addition to the shell mounds, many discoveries of human remains and fragments of ancient Jomondoki pottery have been made. Of these, the Izena Shell Mound is the oldest and largest, to the extent it could be said that the Izena settlement sits atop it. Pendants made from shells have also been discovered, from which it can be surmised the people there led a cultural existence.