English: The remains of a drain located outside the garden depicted in Oshiro Oniwa Ezu, a historic drawing of the old castle garden, have been restored exactly as they were found in an excavation survey. According to the drawing, there was also a flower bed nearby this drain, which is thought to the remains of a stone culvert for channeling rainwater, as mentioned in the "Kinjo Onkoroku" document. Even today rainwater is channeled to the moat through this drain. The stone materials of the culvert include granite for the lid and hard sandstone for the sides.