The Cloister of Ambrius in Geoffrey of Monmouth's Historia Regum Britanniae is a monastery of 300 monks on Mount Ambrius close to Salisbury in which the Saxon Hengist and his followers betayed and slaughtered the British leaders. Bishop Eldadus buried the bodies in a cemetery there. Later Uther Pendragon and Merlin bring the stones of the Giant's Dance from Ireland and set them up as monument to the slain.
The cloister had been founded by one Ambrius many years earlier.
Geoffrey intends his stone monument on Mount Ambrius to correspond to Stonehenge and the cloister of Ambrius on Mount Ambrius to correspond to a religious site in Amesbury, but Stonehenge is about 3.2 kilometres (2.0 mi.) west of Amesbury, and a rise of ground which is much less than anything that one would normally even call a hill, much less a mountain. Amesbury is in a shallow valley of the River Avon.
Wace and Lawman mostly avoid Geoffrey’s precise but incorrect details and take some care that the city of the abbey is not said to be the site on which Stonehenge is constructed, although Wace still mentions that the stones are installed on “the mountain near the burying ground”.
There is no historical evidence of any cloister on or very near the site of Stonehenge. In Amesbury itself, there was the Abbey of St Mary and St Melor, a Benedictine abbey at Amesbury, founded by Alfrida, or Ethelfrida, the Dowager Queen of the Saxon King Edgar. The foundation continued until 1177, when King Henry II dissolved the community because of evil conduct by the Abbess. The buildings were made a cell of the Abbey of Fontevrault, in Anjou; whence a Prioress and 24 nuns were brought and established at Amesbury.
Wace has Hengist and the Britons meet at an predesignated site “near” the Abbey of Amesbury. Similarly the graves of those slain are “near” the abbey. The stones are placed on a mountain “near” the burial ground. Lawman has Hengist and the Britons meet at Ælinge, perhaps Allington, a small place near Stonehenge.