Water was a vitally important resource within a castle. Without fresh water, the defenders of castle could not withstand a prolonged siege. In a large castle like Gifu there would be many wells inside the castle to ensure that there was enough water for drinking and extinguishing fires.
This well was discovered in 1999 during a research excavation, and dates back to when Oda Nobunaga (1534–1582) ruled the castle (1567–1579). The well is around five meters deep and has a square pinewood base at the bottom which supports a lining of closely fitted stones.