Reading a stone cairn on an upland path

Why cairns exist on the hills

A stone cairn is one of the oldest waymarks in the British uplands. You will find them on summits, at path junctions, along old droving routes, and on the edges of steep ground. Some are ancient, some are modern, and some are simply the work of walkers who wanted to leave a mark. Their purpose is usually simple: to confirm a route where a path is faint, or to mark a safe line across open moorland. In clear weather they are a pleasant reassurance. In mist, however, they can become a trap.

The key is to treat a cairn as evidence, not as an instruction. It is one clue among many. A well-placed cairn will sit on a natural line of travel, often within sight of the next one. A poorly placed cairn might be a memorial, a boundary marker, or a random pile left by someone who was themselves lost. Learning to read the difference takes practice, but it is a skill worth developing.

When a cairn tells you the wrong story

Mist changes everything. On a clear day you can see the path ahead, the contour of the land, and the next cairn in the sequence. In fog, you may only see one cairn at a time. That is when the temptation to follow every pile of stones becomes dangerous. I have known walkers on a Welsh hillside follow a line of cairns that led them steadily downhill into a bog, away from their intended ridge. The cairns were real enough, but they marked an old sheep track, not the right of way.

There are other traps. A cairn on a summit may be surrounded by several smaller piles, any of which could be mistaken for the path. A cairn at a cliff edge might mark a viewpoint, not a safe descent. A freshly built cairn, with stones still bright and unweathered, is often the work of someone who was uncertain themselves. And in popular areas, cairns multiply like mushrooms, each one added by a walker who thought they were helping. The result is a confusion of markers that can lead you in circles.

Reading the stones: size, shape, and setting

Look closely at the cairn itself. Size matters: a large, well-built cairn on a prominent point is likely to be a summit or a major route marker. A small, low pile is more likely to be a minor waymark or a temporary one. Shape matters too. A square or rectangular cairn is often a boundary marker. A cairn with a flat top may have been built to hold a map case or a compass. A cairn with a plaque or an inscription is a memorial, and should not be followed as a route.

Then look at the setting. Is there a worn path leading to it? Does it sit on a natural line of travel, such as a ridge, a shoulder, or a col? Is it visible from the previous cairn, and does it point towards the next? Check the ground for erosion: a cairn that has been used as a route marker will usually have bare, trampled ground around it. A cairn that sits in undisturbed heather, with no path, is probably not part of a waymarked route. Finally, look at the lichen and moss. A cairn that is thick with lichen is old and may be reliable. A cairn that is bare and clean is new, and may be misleading.

Map, compass, and the discipline of the bearing

The only reliable way to navigate in mist is to use a map and compass. Cairns are a supplement, not a substitute. Before you set off, identify the cairns marked on your map. Ordnance Survey maps show many, but not all. Use them as checkpoints, not as a handrail. Take a bearing from your current position to the next mapped feature, whether that is a cairn, a stream junction, or a contour line. Then walk on that bearing, using the cairn as confirmation when it appears.

If a cairn is off your bearing, do not follow it. This is where discipline matters. It is easy to think, “That cairn must be the one I want,” and turn towards it. But if your compass says otherwise, trust the compass. A useful technique is to aim off deliberately: set a bearing that takes you to one side of your target, then follow a handrail feature, such as a stream or a wall, to the exact spot. This reduces the chance of overshooting in poor visibility.

Pacing and terrain: the quiet checks

While you walk, keep a count of your paces. On average, a fit adult takes about 60 to 70 double paces per 100 metres on level ground, but this changes with slope, terrain, and fatigue. Use pacing to estimate how far you have travelled, and compare that with the map. If you have walked 500 metres and expected to reach a cairn, but the ground has dropped away, something is wrong. Stop and check.

Also pay attention to the terrain underfoot. If the cairns are leading you downhill when your map shows you should be contouring, or if the ground becomes increasingly boggy when it should be rocky, then the cairns are not marking your route. Trust the land. The shape of the hills, the direction of drainage, and the type of vegetation are all clues that do not lie.

When to walk on by

Sometimes the best decision is to ignore a cairn entirely. Walk on by if it is a single cairn with no clear path, if it sits on a precarious edge, if it is surrounded by eroded ground, or if it does not match your map. Walk on by if it is freshly built or if it is part of a cluster of cairns that seem to lead nowhere. And walk on by if following it would take you off your bearing.

Remember that the uplands are fragile. Leaving the path to follow a false cairn can trample rare mosses, erode peat, and disturb ground-nesting birds such as curlew, golden plover, and skylark. Keep dogs close during the breeding season. Do not add to cairns, and do not knock them down. They are part of the landscape’s history, but they are not a substitute for proper navigation. Use your map, your compass, and your judgement. The stones will still be there when the mist clears.