Portal tombs (sometimes referred to as dolmens) are megalithic monuments which take their name from the two large upright stones which form an entrance or ‘portal’ to the chamber of the tomb. The monuments are generally of a simple rectangular plan with a chamber formed by upright stones and the two portals. The chamber is covered by a capstone which in some cases can be massive. It is believed that portal tombs were once an integral part of a large cairn or mound. These monuments are thought to date to the Neolithic period, and from the available evidence it would appear that they served as communal graves.