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
- Downpatrick Head mainland viewing headland, County Mayo, Ireland (Dún Briste is offshore; this marker is not the car park or a cliff-edge route)
- Coordinates
- 54.32775, -9.34532
- Access
- View Dún Briste from the mainland at Downpatrick Head; visitors do not walk onto the offshore stack. Mayo County Council’s marked loop starts and finishes at the headland car park and crosses grass tracks and gravel. The map marker is the named Downpatrick Head cape on the mainland, not the car park, cliff edge, or route entrance. Mayo County Council warns the headland is exposed and has dangerous cliff edges; supervise children, follow the marked path, and stay well back. Check weather and local notices before setting out.
- Admission
- No ticket or admission charge is listed by Discover Ireland or Mayo County Council. Check current local notices and any parking rules on arrival.
- Time needed
- Allow up to 1 hour for Mayo County Council’s 1.4 km Downpatrick Head loop; the time is for the mainland headland and viewpoints, not access to the offshore stack.
- Best season
- The official tourism and county sources do not name a best season. Choose a calm-weather day and check wind and sea conditions; the headland has exposed, unfenced cliff edges.
- Opening hours
- Discover Ireland and Mayo County Council do not publish fixed opening hours for the headland. Check local notices before travel; the walk is exposed to weather and the cliff edge is hazardous.
- Location checked
- 2026-10-28
- Facts checked
- 2026-10-28
Location
Use the zoom buttons or pinch to zoom. Use arrow keys to pan when the map is focused.
Interactive map loads when in view.
Suggest an edit
No account needed. Your update goes to the editor for review.
Explorer Passport
Next badge: Trail Scout
Unlocked after exploring 5 different unusual places.
0 of 5 places explored
Discover more from Unusual Places
Subscribe to get the latest posts sent to your email.
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?