During my stay in Japan last November, I had one destination in mind that I wanted to visit. It was the Man’nou Pond in Kagawa Prefecture in Shikoku, which was constructed almost by Kobo Daishi Kukai during the Asuka Era, 1,200 years ago. On the way to there, with the advice of a friend, I also visited Sayama Pond in Osaka Prefecture, which was constructed 200 years earlier, around 616 AD. The two major ancient Japanese irrigation reservoirs, the former being the largest and the latter the oldest, are not only significant civil engineering legacies, but also made me reaffirm about what was the expertise I have been involved in all my life, after all.