A circle made of vertical standing stones (megaliths), often surrounding a tomb or religious site. Cromlechs were erected in what is today the UK, Ireland, Brittany (northeastern France), Spain and Portugal, beginning in the Neolithic period, as early as the second half of the fourth millennium BCE. See also: henge, menhir, dolmen.

Plan of Carn Llechart, South Wales, UK. Late Neolithic or early Bronze Age. Royal Commission on Ancient and Historical Monuments in Wales.