Huge, often undressed stone used in various types of Neolithic and Early Bronze Age monuments. The most ancient form of megalithic construction is probably the dolmen, a type of burial chamber consisting of several upright supports and a flat roofing slab. Another form is the menhir, a simple upright stone usually placed with others to form a circle, as at Stonehenge and Avebury in England, or a straight alignment, as at Carnac in France. The meaning of megalithic monuments remains largely unknown, but all share certain architectural and technical features suggesting that their creators sought to impose a conspicuously human design on the landscape and imbue it with cultural symbols. See alsorock art.