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Overlooking Inch Island from the "Grainan of Aileach" ancient stone ring fort, Donegal, Ireland.

The Grianan of Aileach: An Irish Fort Featured on Ptolemy’s Map of the World

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The Grianan of Aileach (Sun Temple of Aileach) is one of the largest and most impressive circular stone hill top enclosures in the whole of Ireland.  The stone fort, which is located in Donegal, Ireland, sits on the top of Greenan Hill, and offers a spectacular view of the surrounding area.

The original structure is generally reckoned to have been built between the 6 th and 9 th centuries AD, though it is believed that the site was already in use as early as 1700 BC. The original stone fort was destroyed during the 12 th century and was restored during the 19 th century.

According to local legend, the Grianan of Aileach was built by the Great God Dagda, who was a member of the Tuatha Dé Danann. These were a race of supernatural beings in Irish mythology who are believed to have occupied Ireland before the coming of the Celts. The Grianan of Aileach is said to have been built by Dagda as a burial monument for his dead son.

Moving from the realm of myth to that of history, it is believed that the fort was built by the Uí Néill, an Irish dynasty that ruled the area between the 5 th and 12 th centuries AD and was used as place where clans would gather to decide important matters. Before the fort was built, however, the site had already been occupied. It has been pointed out that the Grianan of Aileach is one of only two Irish sites marked on Ptolemy’s map of the world, which was produced during the 2 nd century AD.

The Grianan of Aileach. Credit: Ioannis Syrigos

The Grianan of Aileach. Credit: Ioannis Syrigos

The original stone fort did not survive till the present day. In 1101, it was destroyed by Murtagh O’Brien, the king of Munster. In retaliation for the destruction of his royal seat at Kincora, the king of Munster invaded the territory of the Uí Néill, and destroyed their royal seat, the Grianan of Aileach. Murtagh O’Brien supposedly ordered his soldiers to each remove a stone from the structure, so as to leave the Grianan of Aileach in ruins.

The entrance to the ringfort. Credit: Ioannis Syrigos

The entrance to the ringfort. Credit: Ioannis Syrigos

The following centuries were uneventful for the Grianan of Aileach, and the site was left undisturbed until the 19 th century, when it attracted the attention of antiquarians. The site was first formally surveyed in 1830, during which time only a pile of stones remained. The surveyor, George Petrie, reported that the fort measured about 23.5 m (77 feet) across, and he speculated that it would have risen to a height of roughly 2.4 m (8 feet). Petrie also identified the remains of an early Christian church, as well as an even older burial mound. Several decades later, the monument was restored by Walter Bernard, a doctor and antiquarian from Derry.

A view on the inside of the Grianan of Aileach. Credit: Ioannis Syrigos

A view on the inside of the Grianan of Aileach. Credit: Ioannis Syrigos

During the 1860s, Bernard was concerned about the dilapidated state of the site and decided to take matters into his own hands. During the 1870s, a Derry group called the Irish Irelanders, led by Bernard himself, would go to the site each Sunday afternoon to repair and rebuild the monument. The restoration work lasted from 1874 to 1879, and at the end of this period, the Grianan of Aileach acquired its current form. Though Bernard had good intentions in mind, according to the current understanding of the way historical monuments ought to be restored and conserved, the antiquarian over-restored the site.

The outside wall of the Grianan of Aileach. Credit: Ioannis Syrigos

The outside wall of the Grianan of Aileach. Credit: Ioannis Syrigos

In any case, Bernard’s reconstruction has remained till this day, and is the monument that visitors to the Grianan of Aileach today will see. Bernard’s fort is a 5 m (16 feet) high circular structure with three terraces in its interior, which are accessible via stone steps inside the fort. Although the new fort probably bears little resemblance to the original structure, it may be considered to be another phase in the site’s evolution.

Top image: Overlooking Inch Island from the "Grainan of Aileach" ancient stone ring fort, Donegal, Ireland.                     Source: CC by SA 4.0

By Wu Mingren


Carndonagh Community and Rural Development Company, 2018. Grianan of Aileach. [Online]
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coylev, 2018. Grianán of Aileach. [Online]
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Donegal Diaspora Project, 2018. Grianan of Aileach Burt. [Online]
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Failte Ireland, 2018. Grianán of Aileach. [Online]
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National Monuments Service, 2018. Grianán of Aileach, Co. Donegal. [Online]
Available at:, 2018. Grianan of Aileach. [Online]
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Hi All,

Sweet History l enjoyed reading in this article about Supernatural Being's apparently, the great Dagda member of the Tuatha De Danann who built the Grianan of Alieach architecture marvel.

This point in the article stood out to me the most because Dagda a member of The Tuatha De Danann that someone confirms a possibility that the various gods worshipped in the Ancient World were Clans that became their Family Name's.

It was awesome to read that and to know Alexander the Great General Ptolemy after marrying the Pharoah in Egypt Daughter, I suppose that is how it got included in The Map of the Ancient World.

Yeah that's pretty much what stood out to me in this article, to author thanks for Posting this piece to everyone else unto next exciting Discussion regarding a New Subject or Topic, Goodbye!

dhwty's picture


Wu Mingren (‘Dhwty’) has a Bachelor of Arts in Ancient History and Archaeology. Although his primary interest is in the ancient civilizations of the Near East, he is also interested in other geographical regions, as well as other time periods.... Read More

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