Greenan Mountain, home to the ancient An Grianan of Aileach fort in Donegal, offers stunning panoramic views of counties Donegal, Derry, and Tyrone. The fort, dating back to 1700 BC, is steeped in history and provides a perfect spot for a leisurely stroll or a peaceful moment to take in the breathtaking scenery. With its free entry and easy access, Greenan Mountain is a must-visit destination for those seeking a blend of history and natural beauty in Ireland.