The serpentine stone of a circular hill

The Dolmen de Toriñuelo is a circular chamber tomb, located on a farmland two to three kilometres from Jerez de los Caballeros, in the province of Badajoz, Spain. It belongs to the Megalithic age, also known as the Calcolithic or Copper Age. This monument was declared a national monument in 1926 and took on public ownership in 2009. It is oriented in an east-west direction, with a long corridor of access of about 25 metres. Its chamber, slightly oval, is bounded by 13 orthostats. One of these orthostats does not remain in this dolmen. The majority are made of granite and two of them of pizarra. The structure is an artificial hill, raised by the superposition of layers or tunnels of clay and stones, all very compacted layer by layer. The dolmen is covered with a false dome and has a 'Tholoi', or arched passageway - a characteristic feature of the structure.

Sources: Wikipedia, OpenStreetMap, Wikidata, Wikimedia Commons