Yagenbori ( (often referred to in English as “yagura moat”) , one of the shapes used when building moats in Japanese castles, a moat with a V-shaped cross-section. It is called yagenbori because the shape of the moat resembles a yagen, a tool used to grind medicinal herbs.
Yagenbori is very deep and narrow, making it difficult for enemy soldiers to cross the moat and approach the ramparts. The shape also effectively prevents the enemy from using ladders and other siege equipment.
However, over the years, the bottom of the moat has been filled in, and at first glance it more often than not does not look like a yagen. Excavations sometimes reveal it to be a yagen moat.
