Recumbent stone circles are a Scottish invention. The defining feature is the recumbent itself - the largest stone in the ring, laid horizontally on its long side rather than driven upright like the others. Its long axis points always between south and south-west. The two stones flanking the recumbent, the flankers, are usually the tallest uprights in the circle, framing the laid stone like the posts of a gate. Inside the ring there was generally a low ring cairn, though most have eroded away. They were built in the early Bronze Age, possibly developing from the Clava cairns over in Inverness-shire. The closest cousins anywhere else on Earth are the axial stone circles of south-west Ireland, across the Irish Sea. Nobody knows exactly what they were for. Cremated remains have been found inside some. The recumbent stones almost all face the southern horizon, where the moon swings low in its long cycles.

Aikey Brae crowns the summit of Parkhouse Hill, near the village of Old Deer in the Buchan country east of the Aberdeenshire town of Maud. The circle is between fifteen and sixteen and a half metres across. Five stones still stand, including the great recumbent; five more lie fallen. The site was surrounded by conifer plantation for decades, the dark trees pressing in until they were felled in October and November 2019 and the circle could once again be seen from a distance. The view that opens from the brow is the view its Bronze Age builders chose: out over rolling farmland, with the line of the southern horizon laid clean for the moonrise.

When Chris Ball and Richard Bradley excavated Aikey Brae in 2001, they uncovered something the surface had hidden. The ring bank around the circle was edged with kerbstones, and the kerbstones alternated by colour: red and white, red and white, like teeth in a circling mouth. Forty-three pieces of worked stone came out of the ground, with quartz flakes and flint scrapers among them. Radiocarbon dates were anomalous and suggested the Late Bronze Age, later than most of the other recumbent circles. Where some Aberdeenshire circles, like Tomnaverie, show signs of having been built up piecemeal over centuries, Aikey Brae looks like it was put together as a single coherent project. Somebody made a decision, gathered the stones, alternated red and white in the kerb, set the great twenty-one-tonne recumbent in place, and stepped back.

In the 1980s the archaeo-astronomers Clive Ruggles and Aubrey Burl came north and measured Aikey Brae with the rest of the Aberdeenshire recumbents. The pattern they had been chasing held: the recumbent stones all looked out toward the segment of horizon where the moon rides at the southern extreme of its eighteen-and-a-half-year cycle. The flankers framed the rising and setting points of the major lunar standstill. Whether this was ritual, calendar, theatre, or memorial nobody can say with certainty, and the builders did not leave us a manual. But the precision of the alignment is not in doubt. Aikey Brae was made a scheduled monument in 1925, one of the earliest protections of its kind. The stones still face south, the moon still swings low, and the great recumbent still lies waiting for whatever it was meant to receive.