Located on the small keep platform near the entrance to Osaka Castle Keep, the “Kimmeisui Well Roof” was excavated in 1624, when the Tokugawa Shogunate rebuilt Osaka Castle, and the yagata (covered well) was constructed in 1626. The well is approximately 33 meters deep to the surface of the water, and the well casing is made from a single rock. Initially, there was a legend that Toyotomi Hideyoshi sunk gold in the well to remove toxicity from the water, but academic research has confirmed that the well dates back to the Tokugawa period. During the Edo period, it was also called “Koganezui” (golden water) and was regarded as the most important well closest to the castle tower. Today, this wellhouse is designated as a National Important Cultural Property and tells visitors about the history of the period.