The Neolithic people of Great Britain were prolific builders. Just look at the British Isles—they are studded with countless ancient megaliths, hill forts, monumental graves, ritual sites and structures that archeologists have been collectively scratching their heads over for centuries. In Ireland and to some extant, in Scotland, a wholly different kind of structure is found that are as inexplicable as the rest. They are tiny artificial islands known as crannogs built by pounding wooden piles into the beds of lakes and waterways and topping them with dirt. In places where timber was unavailable, such as in the Outer Hebrides of Scotland, crannogs were built entirely of stones. Why did Neolithic people invest so much time, effort and resources hauling stones, some up to 250 kilograms, to build islets at a place where there was no dearth of habitable lands or natural islands is a mystery.

A crannog at Loch Tay, near the Scottish Crannog Centre, Scotland. Photo credit: Ross Murray/Flickr

One theory goes that Ireland at that time was densely wooded, and apart from the upland areas, the lakes were practically the only place where one could see the sky. So the Neolithic people started building homes on artificial islands. Being surrounded by water also protected them from wild animals, so crannogs could also have served a defensive purpose. Many crannogs show signs of habitation and over multiple periods of time, starting from the Neolithic, Bronze and Iron ages, right into Medieval times. During Iron ages, crannogs were probably the centers of prosperous farms, where people lived in an easily-defended location to protect themselves and their livestock from passing raiders. The settlement would have consisted of a farm house, with cattle and crops being tended in nearby fields, and sheep on hill pastures.

Crannogs are pretty widespread in Ireland, with an estimated 1,200 examples, while in Scotland approximately 600 sites have been identified. Actual figures could be higher as a lot of crannogs have now been completely submerged. Many are difficult to distinguish from natural islets, unless properly investigated. Millenniums of disuse have cloaked them with vegetation and now they look like tiny tree-covered islands.

A crannog at Loch Freuchie in Perthshire, Scotland. Photo credit: KAppleyard/Shutterstock.com

In 2012, researchers exploring crannogs in the Outer Hebrides, off Scotland’s western mainland, found Neolithic pottery submerged in the waters around the crannogs. But unlike broken pottery that archeologists are used to finding, these ceramic vessels are nearly intact as if they were deliberately tossed into the water.

Duncan Garrow, an associate professor of archaeology at the University of Reading, who led the research, surmised that the crannogs were used for feasting or funeral rites. Vicki Cummings, another expert in Neolithic monuments from the University of Central Lancashire who was not involved in the study, says these crannogs appear isolated from any known villages or settlements as well as from tombs and burials sites. This suggests that they were used for other rituals, such as coming of age ceremonies.

“Clearly it was not appropriate to take the pottery [brought to the Neolithic crannogs] home,” she says.

Whatever their original purpose in Neolithic times, most crannogs had become dwelling sites by the Iron Age, where generations of people lived.

Eilean Dòmhnuill, on Loch Olabhat, on North Uist, Scotland, may be the earliest known crannog dating to 3200-2800 BC. Photo credit: F. Sturt

A recreation of a Iron-age era crannog as the Scottish Crannog Centre in Loch Tay. Photo credit: John Loach/Flickr

A recreation of a Iron-age era crannog as the Scottish Crannog Centre in Loch Tay. Photo credit: Marc/Flickr