See:
https://www.thejournal.ie/megalithic...82855-Jun2019/

"Carrowmore in the largest cemetery of megalithic tombs in Ireland, with 5,500-year-old passage tombs dating from 3,600 BC. "

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Archaeologists Dr Marion Dowd and Dr James Bonsall directed the excavation of a site that was formerly known as a barrow.Barrows are circular earthen monuments surrounded by a circular ditch. These sites typically date to the Bronze Age and Iron Age, ranging from between 4,000 and 1,500 years old.
The excavation has revealed that some unexpected results – that the monument isn’t a barrow at all.
“Our excavations have revealed that this monument does not appear to be a barrow at all. So far, we cannot find any parallel for it in Ireland,” Dr Marion Dowd said.
The team found that the circular ditch surrounded a central raised area that consisted of a thick circular layer of stone. Inside this was a sunken area with black, charcoal-rich soils."