Giant boulders used by Neolithic cultures (4500-1500 B.C.E.) for building monuments, including tombs. Megaliths are found on Malta island in the Mediterranean Sea, in Germany, in Spain, and in Greece, but their greatest concentration is in northwestern Trance and in the British Isles. Because they were built so long ago, all memory of their original functions has vanished.
All megaliths can be divided into three general types: (1) menhirs, or single stones that stand upright and alone; (2) groups of menhirs, sometimes arranged in circles, semicircles, or parallel lines; and (3) dolmens, three or more menhirs that support a capstone like a roof. If the groups of menhirs are arranged in circles and surrounded by banks of earth, they are called henge monuments, after the most famous megalithic site, stonehenge. Menhir groupings also occur in parallel lines, as at AVEBURY; in multiple parallel rows, as at Carnac in southern Brittany, France; and in fan shapes, as in northern Scotland. Dolmens were occasionally used as tombs, and they also fall into three basic patterns: the single chamber tomb; the passage grave, which has a long corridor that ends in a chamber; and the gallery grave, in which the chamber is enlarged and then subdivided into a number of smaller areas. If the tombs are covered by earthen mounds, they are known as barrows. Some scholars believe that most dolmens were covered at the time of their construction but blame ages of weathering and digging by local residents for wearing away their outer layers. Others believe that many dolmens were never meant to be covered at all.