01 / Manno Pond
The court's own envoy couldn't fix it —Kūkai finished it in under 3 months.
Manno Pond breached in 818, and even the court's own pond-building envoy could not repair it. In 821, on the governor's recommendation, the monk Kūkai took charge, and people flocked to help. Using engineering he had learned in Tang China, he completed the huge pond in under three months. Every June, its "yurunuki" sluice-opening still sends water to the fields, and in 2016 the pond was named a World Heritage Irrigation Structure.

