This looks to me - like a photograph of a Dolmen in County Clare. It sits on the edge of the Burren. It is named Poulnabrone which is the anglicization of its name in Irish language "Poll na mBrón meaning "hole of sorrow" Poulnabrone is classified as a portal tomb. Excavations in the 1980’s revealed the remains of 21 people in the main tomb chamber and radiocarbon dating of their bones indicates that the tomb was in continual use for a period of 600 years between 5,200 and 5,800 years ago. Its pretty old!!! This is a more recent photo of the Dolmen.