A hole of stone, or portal, Dolmens have been perhaps ceremonial bird tables.
Perhaps they were, but not in the sense we might recognise today. As I understand it, dolmens are the stone structures left after the earth and organic materials of burial mounds gradually weathered away over the many millennia. Nevertheless, the idea that souls were transformed into birds is one that is found in many cultures, including the ancient Celtic, Iberian and pre-historic cultures of the Atlantic … So who knows? Perhaps they have indeed become bird tables, of a sort …
Whatever the case, there is definitely something about dolmens that seems so ancient and yet timeless, they do indeed seem like portals.