A dolmen (also known as cromlech (Welsh), anta, Hünengrab, Hunebed, Goindol, quoit, and portal dolmen) is a type of single-chamber megalithic tomb, usually consisting of three or more upright stones supporting a large flat horizontal capstone (table). Most date from the early Neolithic period (4000 to 3000 BC). Dolmens were usually covered with earth or smaller stones to form a barrow, though in many cases that covering has weathered away, leaving only the stone "skeleton" of the burial mound intact.
"Dolmen" originates from the expression taol maen, which means "stone table" in Breton, and was first used archaeologically by Théophile Corret de la Tour d'Auvergne. The etymology of the German Hünenbett or Hünengrab and Dutch Hunebed all evoke the image of giants building the structures. Of other Celtic languages, "cromlech" derives from Welsh and "quoit" is commonly used in Cornwall. Anta is the term used in Portugal, and dös in Sweden.
Megalithic tombs are found from the Baltic Sea and North Sea coasts south to Spain and Portugal. Hunebedden are chamber tombs similar to dolmens and date to the middle Neolithic (Funnelbeaker culture, 4th millennium BC). They consist of a kerb surrounding an oval mound which covered a rectangular chamber of stones with the entrance on one of the long sides. Some have a more complex layout and include an entrance passage giving them a T-shape. It has been suggested that this means they are related to the passage graves found in Denmark and elsewhere.
Dolmen sites fringe the Irish Sea and are found in south-east Ireland, Wales, Devon and Cornwall. In Ireland, however, dolmens are more to be found on the west coast, particularly in the Burren and Connemara, where some of the better-known examples, such as Poulnabrone dolmen, are to be found. Examples have also been found in northern Ireland where they may have co-existed with the court cairn tombs. It is thought that the dolmens themselves evolved from a simpler cist burial method.
A great many examples can also be found on the Channel Island of Jersey, such as La Pouquelaye de Faldouet, La Sergenté and La Hougue des Géonnais. The term Houge is derived from the Old Norse word haugr meaning a mound or barrow. The most famous of these sites is La Hougue Bie, a 6,000 year old neolithic site that sits inside a large mound; later a chapel was built on the top of the mound. 
Amongst the vast Neolithic collections of the Carnac stones in Brittany, France, several dozen dolmens are found. And all around the country, several dolmens still stand, such as the ones of Passebonneau and des Gorces near Saint-Benoît-du-Sault.
Various menhirs and dolmens are located around the Mediterranean islands of Malta and Gozo. Pottery uncovered in these structures allowed the attribution of the monuments to the Tarxien cemetery culture of the Early Bronze Age. This later culture is not to be confused with the Neolithic inhabitants of Malta, who built the Tarxien Temples circa 3100 BC.
In France, important megalithic zones are situated in Brittany, Vendée, Quercy and in the south of France (Languedoc, Rouergue and Corsica). More than 10,000 dolmens and menhirs cover a large part of the country (west and south). Importants menhirs alignments in Brittany (Carnac's alignments count more than 1,000 menhirs)
In Spain dolmens can be found in Galicia (such as Axeitos, pictured below), Basque Country (like the Zorgin Etxea), Navarre, Catalonia (like Romanyà de la Selva or Creu d'en Cobertella), Andalusia (like the Cueva de Menga) and Extremadura (like "Dolmen de Lácara").
In Mecklenburg and Pomerania (Germany) and Drenthe (The Netherlands), large numbers of these graves were disturbed when harbours, towns, and cities were built. The boulders were used in construction and road building. There are still many thousands left today in Europe.
In Bulgaria there are many dolmens, and more are being recorded by archaeologists.
In Turkey, in the Provinces of Edirne And Kirklareli there are dolmens. They have been studied by Prof. Dr. Engin Beksaç since 2004.
Similar tombs can be found all over the world. Korea has many of the Asian dolmens, dating from the 1st millennium BC. The dolmen in Ganghwa is a northern-type, table-shaped dolmen where ancestral rites were held. It is the biggest stone of this kind in South Korea, measuring 2.6 by 7.1 by 5.5 metres. The number of dolmens in North and South Korea, approximately 30,000, is about 40% of the total number of dolmens in the world.
There are also dolmens in Kerala, South India, about 7 km from Marayoor near the small village of Pius Nagar, also known as Alinchuvad. These dolmens are set in clusters of two to five dolmens obviously for the burial of a family. There are hundreds of such dolmen clusters in the area. Apart from overground dolmens, underground burial chambers built with dressed stone slabs have also been discovered in Marayoor. All these dolmens are made from heavy granite slabs, mined using primitive technology. This was a burial ground for several centuries for a noble tribal dynasty known as Adi Cheras, the royal family, which rose as a paramount power in South India in the First Century CE. The Adi Chera tribe traded with the Egyptian and Roman empires of the time. Most of the overground dolmens found in Alinchuvad were made before the Iron Age since no tools were used to dress the granite slabs. On a nearby hill, granite dolmens made, using tools, are also seen. One is underground and the other is overground. The overground dolmen of this type was not used for burial. The length of the dolmens range from 11 ft to 4 ft. There are scores of 4 ft versions of underground type. They had two earthenware pots, one containing the ornaments and weapons of the individual and the other contained the cremation remains. Such underground dolmens are located in various places, like Chelamala,in Ernakulam District, Mattathipara, Muniyara, Panapilavu, etc in the district of Idukki in Kerala State, where Marayoor also is located. It appears that the tribe continued to use this burial practice until the tribe was destroyed in the beginning of third century CE.
Over 3,000 dolmens and other structures can be found in the North-Western Caucasus region in Russia, where more and more dolmens are discovered in the mountains each year.
in County Clare, Ireland]]
A dolmen (also known as cromlech, anta, Hünengrab, Hunebed, quoit, and portal dolmen) is a type of single-chamber megalithic tomb. It usually consists of three or more upright stones (megaliths) supporting a large flat horizontal capstone (table).
Most date from the early Neolithic period (4000 BC to 3000 BC). Dolmens were usually covered with earth or smaller stones to form a barrow, though in many cases that covering has weathered away, leaving only the stone "skeleton" of the burial mound intact.