: Cairns :

A cairn (carn in Irish, carnedd in Welsh, càrn in Scots Gaelic) is a manmade pile of stones, often in a conical form. They are usually found in uplands, on moorland, on mountaintops or near waterways.

In modern times cairns are often erected as landmarks. In ancient times they were erected as sepulchral monuments, or used for practical and astronomical uses.

They are built for several purposes:

They may mark a burial site, and may memorialize the dead.
They may mark the summit of a mountain.
Placed at regular intervals, they indicate a path across stony or barren terrain or across glaciers.
The Inuit erect human-shaped cairns, or inunnguaq as milestones or directional markers in the Canadian Arctic.
In North America, cairns may mark buffalo jumps or "drive lanes."
In North America, cairns may be used for astronomy.
In Norse Greenland, cairns were used as a hunting implement to direct reindeers towards cliffs.
In the Canadian Maritimes cairns were used as lighthouse-like holders for fires that guided boats, as in the novel The Shipping News.
In North America, cairns are often petroforms in the shapes of turtles or other animals.
In the United Kingdom, they are often large Bronze Age structures which frequently contain burial cists
In parks exhibiting fantastic rock formations, such as the Grand Canyon, tourists often construct simple cairns in reverence of the larger counterparts.
They may have a strong aesthetic purpose, for example in the art of Andy Goldsworthy.
They may be used to commemorate events: anything from a battle site, to the place where a cart tipped over.
Some are merely places where farmers have collected stones removed from a field.

They vary from loose, small piles of stones to elaborate feats of engineering. In some places, games are regularly held to find out who can build the most beautiful cairn. Cairns along hiking trails are often maintained by groups of hikers adding a stone when they pass.

**Information copied and pased from Wikipedia [link]