The Nio-mon gate is a magnificent sangen-ikkomon gate (a 3x2-bay gate of an eight-legged style) of the irimoya style (a half-hipped roof) with a tochibuki roof (a type of board roofing in which boards are split along the straight grain and laid in such a way as to have a considerable overlap) has long been said to have been built in 680.
三間一戸、入母屋造、栩葺の堂々たる二王門は白鳳8年（680年）建立されたものと伝わっていた。