Le Barrage

Drop anchor here and you're sitting right beside one of Europe's largest estuarine dams, a genuinely rare feat of engineering where the Vilaine River meets the Atlantic. It's one of only a handful of dams in the world built across an estuary to store freshwater, which makes it worth the stop just to take it in. Watch the boat locks in action as vessels pass through — check the lock schedules online before you arrive so you don't miss the show.