Mont Saint-Michel Pilgrim Causeway, Normandy, France — Pilgrims crossing the treacherous tidal flats to reach the mount risked being caught by the rapidly advancing tide, and many died. The medieval pilgrim route is marked by stakes across the bay, guided by local experts who know the shifting channels and quicksand areas; a causeway bridge replaced the 1879 road dam in 2014.
© Jordiferrer, CC BY-SA 4.0, via Wikimedia Commons
