Dolmen – Irish

I used an Internet sourced image to work from, which said this place is known as Tirnony Dolmen in County Derry, Ireland -its possible the capstone may have collapsed? I need to visit the site for myself.
I chose Derwent Tinted Charcoal pencils, Unison, Schmincke and Florence Printmakers (natural Cumbrian pigment) soft pastels on light grey Pastelmat cut to 24cm square.