#passage graves

Prehistoric large cup and ring petroglyph at ‘Laxe das Rodas’, Galicia, Spain.

Cup and ring marks or cup marks are a form of prehistoric art found mainly in Atlantic and Mediterranean Europe. They consist of a concave depression, no more than a few centimetres across, pecked into a rock surface and often surrounded by concentric circles also etched into the stone. Sometimes a linear channel called a gutter leads out from the middle. The decoration occurs as a petroglyph on natural boulders and outcrops and also as an element of megalithic art on purposely worked megaliths, and on some stone circles and passage graves.-wikipedia.com