We do not know what the people who placed these stones were doing. They came from the Bronze Age - between roughly 2000 and 800 BCE - and they did not leave instructions. The Scots writer and engineer Alexander Thom argued, in his 1971 book Megalithic Lunar Observatories, published by Oxford University Press, that the rows worked as an astronomical instrument: the fan pattern matched the standstill positions of the moon as it crept north and south along the horizon over its 18.6-year cycle, and the northern view from Mid Clyth points at the Banffshire hills, 80 kilometres across the Moray Firth, where the southernmost moonrise of that cycle would have appeared. It is a beautiful theory. It is also disputed. More than twenty similar stone rows are now known across Caithness and Sutherland, and none of the others align in a way that supports the lunar reading. The case for Mid Clyth as an observatory remains exactly what it was when Thom proposed it: possible, undeniable in some details, unprovable in the rest.

What makes the Caithness stone rows strange is their geography. Standing stones of various kinds appear all over Britain, but rows of this particular type - low, numerous, set in fans on hillsides - are found only in Caithness and Sutherland. They have no British relatives. Their closest analogues are in Brittany, on the far side of the English Channel, where similar rows survive though with much taller stones. The Brittany alignments at Carnac are tourist landmarks; the Mid Clyth stones lie a kilometre off a back road, with no shop, no fence, and usually no one to ask about them. The shared archaeology between northern Scotland and western France is a puzzle: a Bronze Age cultural connection that left these matching marks across a thousand kilometres of sea, then went silent. We have no script to read, no names to repeat, no festivals to recover. We have rows of stones.

Walking among them is curiously quiet work. The stones do not rise above the heather and bracken, so they read at first as natural - shed glacial debris, perhaps, or the remains of a wall - and only when the eye registers the pattern do they become a monument. The site sits at about 100 metres above sea level, with the North Sea visible to the east and the broad sweep of Caithness farmland behind. In summer the larks rise from the surrounding fields. In winter the wind comes straight off the water and the stones look like a flock of cold sheep that have stopped to consider something. Whoever placed them must have intended a sight line, but stood with the moon, not for any audience. They left the answer in geometry, and the geometry has half-survived. The rest belongs to the hillside.