Onna-bori
Japan
The Onna-bori was an irrigation canal dating the from Heian period, the remnants of which are located in what is now the cities of Maebashi, and Isesaki, Gunma Prefecture in the northern Kantō region of Japan. The six surviving disconnected portions were collectively designated a National Historic Site of Japan in 1983.
Canal data from Wikidata (CC0). Summary from Wikipedia (CC BY-SA).