How is this sort of thing formed?
Desire Paths
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
People traveling through this area, riding on horse-drawn carriages over the course of several centuries.
Holy shit that makes it even cooler
Patience pays off, thank you
This is cool, but it's not really a desire path
This seems like an odd formation to occur naturally. Is it a trench?
This is what centuries old desire paths look like. Or it's an old (non-standard?) railway.
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).