Cairn or Cairns
Cairn: A pile of rocks used to indicate a route or a summit. Historically they were erected as sepulchral monuments. Popular on Whistler hiking trails as trail markers in the alpine where the lack of trees doesn't allow for tree markers. Build on ledges or on the high side of a trail they can be seen after the trail has been obscured by snow.
Cairns Along the Ancient Cedars Trail in Whistler