grianan of aileach or greenan fort. inishowen. county donegal. ireland

aileach ancient archaeological architecture building celt celtic circle circular countryside county culture defence defensive donegal eire europe excavated exterior field fort fortified fortress green greenan grianan head heritage hill hills hilltop historic historical inishowen ireland irish landmark medieval megalithic monument mound mounds national nature neolithic old open outdoor outdoors outside past peninsula prehistoric remains ring ringfort river round route ruin ruined ruins rural scenic settlement sight site solid stone strength strong tara temple tourism tourist tower travel valley view wall