grianan of aileach, ancient drystone ring fort, part of prehistoric structures complex, located on top of greenan mountain in

architecture prehistoric structures historical concentric inishowen landscape panoramic structure peninsula gaeltacht drystone mountain landmark building atlantic grianan aileach ancient complex located greenan donegal ireland scenery tourism tourist flyover larger aerial swilly meadow nature scenic temple palace travel europe cashel county circle lough orbit ruins rural stone irish derry grass green drone ring fort site view iron wild wall hill top sun age ely