The construction period of these monuments is located in recent prehistory, with dates ranging from 3500 to 2000 BC. c.

The cromlechs, like all megalithic monuments, were essentially funerary in nature, that is, necropolises.

Some researchers go so far as to support astronomical theses, suggesting that they could have been observatories of the stars or the cycles of the Moon. These assumptions, although possible (for example in Stonehenge, much studied in this sense), have not yet been reliably demonstrated and are received with great caution by the scientific community.

Dimensions vary from site to site. In France you can visit cromlechs with diameters greater than 100 meters (such as the Crêperie de Carnac in Brittany and those of Rigalderie and Peyrarines in the Gard). The menhirs that form the cromlechs vary in France between one and more than three meters high. Some Scottish cromlechs exceed four meters in height.

There are notable cromlechs in the British Isles, especially in Scotland (e.g. Achmore and Callanish Stones in the Hebrides; the Rocks of Stenness and the Ring of Brodgar in Orkney) and in Cornwall, although they also exist in other areas of Europe, such as Portugal.

One of the most famous in the world is Stonehenge, made up of several concentric circles, and one of the oldest in Europe is Castlerigg, both in England.

Outside the European continent, there are stone circles in Africa (Senegal, Gambia, Ghana, Ethiopia, Algeria) but they cannot be considered cromlech stricto sensu since they were built only a few centuries ago. And, according to the commonly accepted definition, cromlechs are always prehistoric constructions.

In France, cromlechs are known in Brittany (St. Peter's Cromlech in Saint-Pierre-Quiberon, or that of the island of Gavrinis[4]​, both in the Morbihan, or at the extremes of the Carnac Alignments), in Aquitaine and in Languedoc (at the site of Causse de Blandas ("near the Cirque de Navacelles"), in the Gard there are three of the four cromlechs in the region). In the French Basque Country there are stone circles of small diameter (about ten meters) but it is believed that in fact they are only the circular outlines of ancient burial mounds that have been razed. There is also a cromlech of about 70 meters in diameter in the Petit-Saint-Bernard"), on the Franco-Italian border between Savoy "Savoy (department)") and the Aosta Valley.

There is also a cromlech on the plateau des Combes") above the cham des Bondons"), Lozère. The most majestic of its menhirs is known as the "Menhir of the three parishes", due to its geographical position, on the borders of three parish churches of the Ancien Regime.

There is also a cromlech in Sailly-en-Ostrevent, in the Pas de Calais "Pas de Calais (department)").

In Portugal there is the most important cromlech on the Iberian Peninsula, the Almendros Cromlech, about 12 km west of Évora. It has several enclosures, one of them formed by three circles of menhirs and about 18 meters in diameter, and another oval, 43.6 meters long axis by 32 meters short axis.

There are also many monuments of this type in the central and western Pyrenees, whose name in Basque is harrespil, which means "circle of stones." Its similarity with other European cromlechs lies in the shape (circles of stones stuck in the ground), but they are small in size: there are some whose diameter does not reach three meters, and there are few with more than fifteen. Its stones are also small. The circles, in general, are grouped in variable numbers, and are located on rounded hills and summits. Sometimes a cromlech surrounds a mound or even a dolmen.

The Pyrenean cromlechs are associated with the Iron Age (first millennium BC). In excavations carried out, its funerary function has been proven. The corpses were previously cremated, and their ashes were placed in ceramic vessels, or surrounded with small slabs (forming a cist).

Its geographical distribution covers the entire central and western Pyrenees, both north and south. It has a characteristic not yet explained: to the west they end abruptly when they reach the Oria and Leizarán rivers. In the eastern part of the basin of the latter river there are a significant number of cromlech, but in the western part there is not a single one. To the west of these rivers, very few, isolated and dispersed specimens have been located (1 in Álava, 5 in Vizcaya and 3 in Navarra).

The construction period of these monuments is located in recent prehistory, with dates ranging from 3500 to 2000 BC. c.

The cromlechs, like all megalithic monuments, were essentially funerary in nature, that is, necropolises.

Some researchers go so far as to support astronomical theses, suggesting that they could have been observatories of the stars or the cycles of the Moon. These assumptions, although possible (for example in Stonehenge, much studied in this sense), have not yet been reliably demonstrated and are received with great caution by the scientific community.

Dimensions vary from site to site. In France you can visit cromlechs with diameters greater than 100 meters (such as the Crêperie de Carnac in Brittany and those of Rigalderie and Peyrarines in the Gard). The menhirs that form the cromlechs vary in France between one and more than three meters high. Some Scottish cromlechs exceed four meters in height.

There are notable cromlechs in the British Isles, especially in Scotland (e.g. Achmore and Callanish Stones in the Hebrides; the Rocks of Stenness and the Ring of Brodgar in Orkney) and in Cornwall, although they also exist in other areas of Europe, such as Portugal.

One of the most famous in the world is Stonehenge, made up of several concentric circles, and one of the oldest in Europe is Castlerigg, both in England.

Outside the European continent, there are stone circles in Africa (Senegal, Gambia, Ghana, Ethiopia, Algeria) but they cannot be considered cromlech stricto sensu since they were built only a few centuries ago. And, according to the commonly accepted definition, cromlechs are always prehistoric constructions.

In France, cromlechs are known in Brittany (St. Peter's Cromlech in Saint-Pierre-Quiberon, or that of the island of Gavrinis[4]​, both in the Morbihan, or at the extremes of the Carnac Alignments), in Aquitaine and in Languedoc (at the site of Causse de Blandas ("near the Cirque de Navacelles"), in the Gard there are three of the four cromlechs in the region). In the French Basque Country there are stone circles of small diameter (about ten meters) but it is believed that in fact they are only the circular outlines of ancient burial mounds that have been razed. There is also a cromlech of about 70 meters in diameter in the Petit-Saint-Bernard"), on the Franco-Italian border between Savoy "Savoy (department)") and the Aosta Valley.

There is also a cromlech on the plateau des Combes") above the cham des Bondons"), Lozère. The most majestic of its menhirs is known as the "Menhir of the three parishes", due to its geographical position, on the borders of three parish churches of the Ancien Regime.

There is also a cromlech in Sailly-en-Ostrevent, in the Pas de Calais "Pas de Calais (department)").

In Portugal there is the most important cromlech on the Iberian Peninsula, the Almendros Cromlech, about 12 km west of Évora. It has several enclosures, one of them formed by three circles of menhirs and about 18 meters in diameter, and another oval, 43.6 meters long axis by 32 meters short axis.

There are also many monuments of this type in the central and western Pyrenees, whose name in Basque is harrespil, which means "circle of stones." Its similarity with other European cromlechs lies in the shape (circles of stones stuck in the ground), but they are small in size: there are some whose diameter does not reach three meters, and there are few with more than fifteen. Its stones are also small. The circles, in general, are grouped in variable numbers, and are located on rounded hills and summits. Sometimes a cromlech surrounds a mound or even a dolmen.

The Pyrenean cromlechs are associated with the Iron Age (first millennium BC). In excavations carried out, its funerary function has been proven. The corpses were previously cremated, and their ashes were placed in ceramic vessels, or surrounded with small slabs (forming a cist).

Its geographical distribution covers the entire central and western Pyrenees, both north and south. It has a characteristic not yet explained: to the west they end abruptly when they reach the Oria and Leizarán rivers. In the eastern part of the basin of the latter river there are a significant number of cromlech, but in the western part there is not a single one. To the west of these rivers, very few, isolated and dispersed specimens have been located (1 in Álava, 5 in Vizcaya and 3 in Navarra).