The stone itself is a glacial erratic - a block of Devonian Old Red Sandstone left here by the retreating ice tens of thousands of years before any human laid eyes on it. It measures 8.6 metres long by 4 metres wide by up to 2.5 metres high. It sits alone in a steep-sided U-shaped valley between Quoys and Rackwick on northwest Hoy, the slopes of Ward Hill rising to the east, the peatland brown and wet around it. A boardwalk now leads to it from the lane, and you can crouch and crawl inside. The entrance is a one-metre square cut from the west face. The passage runs straight in. Two side cells open off it, each about 1.7 metres by 1 metre. In the southern cell, the inner end is shaped into a kind of pillow - a slight rise of uncut rock left in place by whoever carved the chamber.

Why anyone would choose this method - so much harder than the usual approach of stacking slabs into a cairn - is a question archaeologists have argued over for two centuries. The Dwarfie Stane bears a striking resemblance to Neolithic and Bronze Age rock-cut tombs around the Mediterranean. One theory is that the idea of rock-cut tombs spread north along the Atlantic coast, and Hoy's builders tried it once. The folklorist Hugh Miller, who was a working stonemason himself, was the first to point out that the Old Red Sandstone here is exceptionally compact - meaning the work would have been brutal even with metal tools, never mind the antler picks of the time. The archaeologist R. Castleden later suggested the experiment was "tried once and found to be unsatisfactory." Nobody built another.

Someone broke in through the top. The original entrance was sealed by a stone slab that now lies on the ground in front of the tomb, but at some unknown date, plunderers smashed through the roof to reach whatever was inside. By the sixteenth century the hole was already there - the antiquarian Jo Ben mentioned it in 1529. Historic Environment Scotland repaired the breach with concrete in the 1950s or 1960s, and the visible patch is still there. Whatever was originally placed inside the tomb - bones, grave goods, whatever the Neolithic farmers of Hoy chose to leave with their dead - was taken so long ago that no record survives.

In 1850 a British army officer named Major William Mounsey carved an inscription into the rock above the entrance. It is in Persian calligraphy - Mounsey was a former spy and intelligence officer who had served in Afghanistan and Persia and was clearly proud of the languages he had learned. Translated, it reads: "I have sat two nights and so learned patience." He meant the midges. Above the Persian line, he carved his own name backwards in Latin - a little trick he liked. The graffiti is now itself protected as part of the monument's history. The midges, predictably, are still there. Anyone who has spent a still summer evening on Hoy can confirm that two nights would teach you patience, or possibly something else entirely.