The people buried here were cremated. What a cairn conceals, when archaeologists open one, is usually burnt bone, and of the eight cairns excavated at Sammallahdenmäki, six held human remains - about as direct a confirmation of purpose as prehistory offers. Cremation and cairn burial were both innovations that arrived with the Bronze Age in this part of the world, and both outlasted it, carrying on well into the Iron Age.

Building one was heavy work. The granite came from the cliff face below the ridge or was gathered off the surface nearby, boulder by boulder, then stacked by hand into forms that have held their shape for three thousand years. Nobody knows how many people it took, or how long, or who was entitled to one. What is clear is that a family burying its dead this way spent an enormous amount of labour on a monument whose entire function was to be looked at from a distance.

The graves span roughly a millennium and a half. The World Heritage inscription dates the cairns between about 1500 and 500 BC, with the youngest reaching forward into the early Iron Age - generation after generation returning to the same ridge, working in clusters along its crest, adding to what their great-grandparents had begun.

That persistence is itself the evidence. Archaeologists read the cairn groups as a claim of kin-group ownership over land, the kind of claim worth making once people farm rather than follow game. Across those same centuries the climate in Satakunta was turning colder and wetter; broadleaf woodland gave way to spruce, and livelihoods leaned further into cattle and crops. Some researchers connect the cairns to sun-worship rituals that spread across Bronze Age Scandinavia. It is a plausible reading of a hilltop chosen for its sky and its sightlines, and it is not provable.

Two of the graves resemble nothing else on the ridge. The *Kirkonlaattia*, or Church Floor, is a flat rectangular cairn about sixteen by nineteen metres, laid out so evenly that later Finns thought it looked like the floor of a large hall and named it for that. The Finnish Heritage Agency calls it unique in Finland and in all of Scandinavia. The *Huilun pitkä raunio* - the Long Ruin of Huilu - runs roughly twenty-four metres by eight, a low wall-like grave enclosed by a stone wall of its own.

Both names are modern inventions. Whatever the builders called these structures, and whatever set the people inside them apart from the neighbours under ordinary round cairns, went unrecorded. The forms survive. The reasoning does not.

The cairns first enter the written record in 1878, in a catalogue of ancient sites, accompanied by a vague note about an excavation whose details have been lost completely. In 1891 the archaeologist Volter Högman opened four of them, including both the Church Floor and the Long Ruin of Huilu. Further excavation followed in 2002.

Counting them is oddly difficult. The Finnish Heritage Agency lists thirty-six cairns; UNESCO's own summary says only 'more than 30'; much of the older literature settles on thirty-three. UNESCO inscribed the site in December 1999 under criteria (iii) and (iv) - exceptional witness to the society of Bronze Age Scandinavia, and an outstanding example of Bronze Age funerary practice - which made it the first prehistoric archaeological site in Finland to join the list.

Sammallahdenmäki lies about twenty kilometres east of central Rauma, reached on a marked forest trail that climbs onto the ridge and follows its crest past the cairn clusters; guided tours run in season. Nothing has been reconstructed. What you get is grey granite under moss, on ground that lifted itself out of the sea and then kept going.

It is a burial ground, and it rewards being walked as one. The families who carried their dead up here wanted them somewhere high, somewhere visible, somewhere the living would have to look at on the way in from the water. Three thousand years later, in a landscape that no longer cooperates, that intention is still perfectly legible.