Dún Briste – Ireland’s Dramatic Sea Stack Split From the Mainland
In the Irish town-land of Knockaun, 80 meters off Downpatrick Head stands a colossal, 50 meters in height, sea-stack called Dun Briste (The Broken Fort). The surrounding cliffs, including the rock formation, were formed about c. 350 million years ago, when the sea temperatures were much higher than today.
Every year, Downpatrick Head is visited by birdwatchers who come to observe and record the many different species on the stack.
Poll na Seantoine, a cave, which has been hollowed out by the strong waves of the Atlantic Ocean, is a magnificent sight.
There are few folk tales about how the sea-stack became separated from the mainland. According to one of them, on the place where the stack now stands used to live an ogre Geodruisge, He was a most obnoxious character, often making life difficult for St. Patrick, who used to pray at the church on Downpatrick Head. The saint became agitated, and prayed to God to get rid of this tyrant. The next day the stack with the ogre’s residence was separated from the mainland. Geodruisg couldn’t escape and so he vanished.
Photo by depositphotos.com
Photo by depositphotos.com
However, a passage in the journal by MacFirbis is a more likely explanation. It describes the cutting off, of the rock of Duross promontory by the sea. The residents were taken off using ship ropes in 1393.
A few years ago, a helicopter landed several scientists on the stack; they were the first humans to set foot there for ages. They stayed there overnight and examined the surface where they found the remains of a medieval house, walls, cultivation ridges, and a corn grinding stone.
The view at Downpatrick Head is breathtaking; on a sunny day the coastline of counties Donegal and Sligo are visible, but caution is needed when approaching the cliff edge.
Dun Briste is a unique and beautiful natural wonder, and a visit to this sea stack is a must for anyone interested in Irish folklore, history, and natural beauty.
UnusualPlaces Field Notes
- Location
- Dún Briste — mainland viewing area at Downpatrick Head, County Mayo, Ireland
- Coordinates
- 54.3279909, -9.3452622
- Access
- View the offshore sea stack from the Downpatrick Head coastal walk; the headland also has a blowhole viewing platform
- Time needed
- Allow 30 minutes–1 hour at Downpatrick Head
- Location checked
- 2026-09-24
- Facts checked
- 2026-09-17
Location
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Thanks for the beautiful pictures! I’m proof reading a friend’s historical fiction novel that winds up in Ireland with a reference to Acjill island and the monoli8Dun Bridge. Glad I googled it!
It would be interesting to know more about the composition of the different layers of rock represented in the Dun Briste Sea Stack. Corresponding those layers with the approximate period of time when they were formed. From the information provided, the stack and surrounding area were formed a whopping 350 million years ago. In a way, time on earth is similar to the vast distances of the universe. 350 million years is a long time, but in geological terms, not that long when contrasted with rock formations found elsewhere that are almost as old as the earth itself, several billions of years and more.
That very distinctive lighter layer was formed at the time of the cataclysmic event that wiped out the dinosaurs. You will find this same layer, sometimes lighter, most often darker as you draw closer to the crater itself, all over the world.
What is your source of this information?