Iwashita Ishihane Ruins

Iwashita Ishihane consists of three stone drawbridges. They were said to have been built by Kato Kiyomasa around 1605 for the flood control of Midori River. These bridges appear in a drawing of Edo period, and they are called "Ichi no Hane the first drawbridge," "Ni no Hane the second drawbridge," and "San no Hane the third drawbridge." According to the drawing, the first drawbridge is about 211 meters long, the second one is 124 meters, and the third one is 286 meters. The total length is as long as 624 meters. Iwashita Ishihane Ruins weakened the water pressure in flood with the intermittent stone walls and a bit-shaped embarkment called "Kutsuwadomo"that was used as a flood retarding basin.
The stone drawbridges at Iwashita Ishihane Ruins were found during the construction of the bank in November, 2003. At the Ni no Hane, some rare and important structural remnants were discovered, such as stone walls with Sangizumi technique and Yasesumi technique from early Edo period, using small or large stone blocks at the corner of the stone walls. There were also stones with letters in red ink discovered here, a very rare case in Japan.
The current stone wall around a sluice was built after the construction in 2003, but you can still see the original stone drawbridge at the upper and lower courses of Midori River. The ruins are very important to learn the techniques for flood control and engineering works in the early Edo period and the history of Midori River.