A stone circle is a circular alignment of standing stones. They are commonly found across Northern Europe and Great Britain, and typically date from the Late Neolithic and Early Bronze Age eras, with most concentrations appearing from 3000 BC. The best known examples include those at the henge monument at Avebury, the Rollright Stones, and elements within the ring of standing stones at Stonehenge. Ancient stone circles appear throughout Europe, with many existing in the Pyrenees, on the Causse de Blandas in southern France in the Cevennes, in the Alps, Bulgaria, and Poland. Another type can be found in the Horn of Africa.