This was the storehouse for gold and silver coins of the Tokugawa government. Although it is said that the two-storied Treasure House was built in 1625 and was remodeled into a single story structure in 1837, this assumption has not been verified. he lower section of the external wall is finished with Namako-kabe (a wall in which square and flat tiles are affixed with nails and the masonary joints plastered in a semicircular mount). Fire-prevention, moisture-proofing, and burglar-proofing devices are installed at the door, the windows, the floor and the ceiling.