There's a castle with a moat that's a canal
In the 19th century, the British government ordered the drainage of the moat surrounding the medieval castle of Arundel in West Sussex, England. However, the local canal company, which was building a new waterway nearby, convinced the government to redirect the moat's water into the canal instead. Today, the Arundel Castle's moat is actually a canal, 400 meters long and 1.5 meters deep, connecting the castle to the River Arun.