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A hollow way in La Meauffe, Manche, France
(sh.itjust.works)
Desire paths Desire paths can be paths created as a consequence of erosion caused by human or animal foot-fall or traffic. The paths usually represent the shortest or most easily navigated routes between origins and destinations. https://en.wikipedia.org/wiki/Desire_path
This seems like an odd formation to occur naturally. Is it a trench?
It’s a “sunken lane” or “hollow way,” and it’s most likely caused by a few hundred years of very specific erosion (amusingly the lead image for the Wikipedia article for this phenomenon is the same as the post).
This is what centuries old desire paths look like. Or it's an old (non-standard?) railway.