Cairn

Cairn along Trail 74 in the Gila National Wilderness in southern New Mexico.

From Wikipedia:

Cairn is a term used mainly in the English-speaking world for a man-made pile (or stack) of stones. It comes from the Scottish Gaelic: càrn (plural càirn). Cairns are found all over the world in uplands, on moorland, on mountaintops, near waterways and on sea cliffs, and also in barren desert and tundra areas. They vary in size from small stone markers to entire artificial hills, and in complexity from loose, conical rock piles to delicately balanced sculptures and elaborate feats of megalithic engineering. Cairns may be painted or otherwise decorated, e.g. for increased visibility or for religious reasons.

In modern times, cairns are often erected as landmarks, a use they have had since ancient times. Since prehistory, they have also been built as sepulchral monuments, or used for defensive, hunting, ceremonial, astronomical and other purposes.