Grianan of Aileach is an ancient stone fort. It stands a top a hill - a site on which a fort has stood for three millennia.
This view from the Walls of Grianan of Ailach opens looking towards Inch Island, in Lough Swilly. As we start to rotate to the left we pass along Lough Swilly taking in the lights of Letterkenny and then the small ribbon of the river Foyle under the sunrise near the town of Strabane.
As we continue to rotate we pass the hill-tops of Hollywell Hill - with the RTE (Irish TV) transmission mast and Sheriff's Mountain with the BBC (British TV) transmission mast. The border, partitioning Ireland into Northern Ireland and the Republic of Ireland, runs between the two transmitters.
Next we glimpse the River Foyle again and some of the lights of the City of Derry - most of the city is obscured by the hills. Then Lough Foyle gives way to Scalp Mountain, and beyond it we return to our starting point at Lough Swilly.
The panorama encompasses three counties: Donegal, Derry and Tyrone.
Inside the fort you can see the three tiers of terracing within the walls.
What is more remarkable is that forts of near identical design stand in West Donegal and on the Aran Islands
. This suggestis that the original fort was not just the result of the efforts of an early group of skilled dry-stone-wallers, but the product of a sophisticated culture with architects, communication and planning.