A cairn is a human-made pile (or stack) of stones. The word cairn comes from the (plural ). Cairns are used as trail markers in many parts of the world, in uplands, on moorland, on mountaintops, near waterways and on sea cliffs, as well as in barren deserts and tundra. 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, whether for increased visibility or for religious reasons. An ancient example is the inuksuk (plural inuksuit), used by the Inuit, Inupiat, Kalaallit, Yupik, and other peoples of the Arctic region of North America. These structures are found from Alaska to Greenland. This region, above the Arctic Circle, is dominated by the tundra biome and has areas with few natural landmarks.