Of all of the kinds of chambered tomb that are found in Britain and Ireland, dolmens are perhaps the most iconic – and the least understood. Yet their composition is very simple: to create a dolmen, you simply place a large slab or ‘capstone’ on top of three or more upright stones, creating an open, box-like chamber. So far, so straightforward – except for the small matter of raising the capstone. In order to get a better idea of how these dolmens were engineered, we began a campaign of excavations at Garn Turne Major in Pembrokeshire, home to the largest surviving capstone from a British megalithic monument.
Weighing in at around 80 tonnes, the Garn Turne Major capstone is a truly massive slab of rock. To put this in perspective, the great sarsen stones at Stonehenge weigh on average 25 tonnes. But even Garn Turne cannot compare with the absolutely colossal capstone at Brownshill, Co. Carlow (Kernanstown), which at 160 tonnes ranks as one of the largest known anywhere in Europe.
Tomb with a view
Building these mighty monuments using prehistoric technology was an incredible feat – something their proud creators were apparently eager to highlight. The capstones often balance precariously on the tips of the supporting slabs beneath. Was this showboating designed to draw attention to the prowess of those assembling sites like these? To us, this delicate arrangement indicates that the cairn material sometimes found around such monuments served a radically different purpose to the traditional view: these are not the vestiges of a lost burial mound, but packing to keep the uprights in place.
