Whoever’s gone out hiking will have seen cairns: stacks of stones to mark a trail. I love the way they look and the function they have. People seem to also make cairns for fun. While it can be fun to create, personally I wouldn’t do that. You never know if you send someone astray by placing a random mark along a trail or by taking away from an existing purposefully placed cairn. The only place I added to a cairn was at a place along the Vasaloppsleden trail in Sweden (Bordet). It’s kind of a thing to add a stone there, for good travels or something like that (I don’t remember exactly).
I love how the use of stones and stacks of stones to mark a route or trail is such an old practice. They did it in prehistory and we still do it today. People are quite the habitual creatures, aren’t they?