The ruins discovered in a section of the Inner Palace of Heijo Palace were designated as a Special Historic Site in 1952. These ruins are preserved by a large-span steel frame structure with a span of 26×28 meters. A lightweight ceiling curtain is suspended from the large roof with deep eaves that seem to spread out like wings, achieving the effects of heat insulation and alleviating sunlight exposure. The buildings, which have been designed several times, are connected by corridors to ensure the unity of the design. Currently, within the "Heijo Palace Ruins Historical Park", it serves as the "Ruins Exhibition Hall" and is open to the public along with relevant materials in the form of an "Exposed Exhibition", which preserves the ruins in their original state.