Underground Dublin, Part II: The Mines of Dublin

This is part two in a two part series, which came to fruition as a result of limited freedom of movement during the Coronavirus lockdown. It is very different to my usual articles, and its style and content may be a ‘required’ taste. For me, the cave always directs the ‘story’ and I hope that you will bear with me in what is an attempt to create something new and positive from a time of speleological stagnation. Part one deals with Dublin caves and can be found here.

Dedicated to Matthew Parkes, who had the greatest of enthusiasm for even the most minor of caves and mines, and who was always eager to share his inexhaustible knowledge – as can be seen here by the many references to his work. Ní easbha go dích cáirde. Ar dheis Dé go raibh a anam.


Prior to the 18th century, mining was slow to develop in Ireland. At the time, ownership of mineral resources was maintained by the British Crown, whose concern for the limited workings in Ireland, during a time of national unrest, were minor. By the early 18th century, however, royal decree allowed for private interests to develop mines and with this, Dublin began to develop a small but capricious mining industry.1

The adit at Smugglers’ Cave, Loughshinny
Smugglers’ cave, loughshinny

One of the first mines was established at the coastal village of Loughshinny. In the late 1700s, this mine initially yielded an impressive fifty seven tones of copper ore, with great ease. However, a half dozen more attempts would be made over the following two hundreds years, to extend the mine’s potential. A series of vertical shafts close to the village were dug and small sections of multilevel stopes progressed. Though more ore would be recovered, the mines were poorly managed and frequently abandoned. The impossible task of keeping the mines secure from the incoming tide remained a difficulty that could not be resolved.1 Today, most of the mine shafts are invisible, having been infilled and grown over. However, one short section of mine is still accessible.

Smugglers’ Cave

Smugglers’ Cave is a mine adit which runs from the shore line into the low cliffs, north of the village. It is cut into sandstone bedrock and runs for approximately 30 meters. It is relatively featureless, lacking any sign of industrialisation, and one could be forgiven for thinking it a natural cave. Despite its short length, it is held in folk memory as a hide-out during the late 18th century for a number of smugglers, who raided ships from Rush and Skerries, and stored their stolen goods here.

The most famous of smugglers was ‘Jack the Batchelor’ who, taking advantage of the “heavy tax on the wine and silk that came into the country from France, Jack and his men used to smuggle in the wine and cover them with herrings.”2 Jack the Batchelor, who was buried locally at Kenure Cemetery, left “hoards of gold, silks, laces, wines and skins hidden in [the] underground passage”.3 I can report, however, no success in finding such. It is perhaps not surprising that such a place might entice folk imagination and, it is recorded that:

About forty years ago a deaf and dumb man lived in the caves. He used to go to the village of Loughshinny for his his food. After a time he did not come at all. The people were afraid that he had died in the cave. But it is said now that a serpent carried him away.4

If you ask me, I think it would be preferable to die in a cave than to be carried away by a serpent! Loughshinny is perhaps better known for its above ground limestone geology than it is for its mines. South of the village can be seen a very fine example of pressure folded sedimentary beds. These are limestone and shale beds which are folded into a distinctive ‘M’ in section, composed of anticlines and synclines.

Loughshinny folds
decco’s cave, dalkey

The mining history of Dalkey, on the southside of Dublin Bay, somewhat mirrors its northern counterpart of Loughshinny. Exploration of Killiney Hill was begun in 1751 for lead, barytes and smaller quantities of copper. Shafts were dropped and ore was recovered, as adits were dug from the seashore cliffs of Vico beach. After an initial enthusiasm, Dalkey would prove to be difficult and relatively unfruitful, as the nearby mines of Ballycorrus became the primary focus on the southside of the city.1 Dalkey faced similar problems to those found in Loughshinny. It suffered from yields which, while occasionally large, were short term. Added to this was the constant ingress of sea water, which saw the mines ceasing and reopening over the following centuries.5

Decco’s Cave

Another similarity shared with Loughshinny is Dalkey mine’s story of having an itinerant occupant. In this case, it was a recent event in which ‘Decco’:

“slept on an iron bed and that it still remains in the cave. Som(e)one is supposed to have found him dead in the cave one morning.”6

Another local source notes in 1941 that:

This cave was home some 30 years ago of “Decco”, as he was always known locally, and is still remembered in the name of the cave to-day “Decco’s Cave”. His right name is doubtful but I believe it to have been Tom Kavanagh… He had been a sailor and slept in a hammock up in the cave. I regret to say as boys we often jeered in at him to rouse his ire, which we never failed to do, with the expected result that “Decco” would seize an axe and chase us far up the strand, breathing fierce imprecations. I now apologise to his memory for our thoughtless cruelty- though if he had ever caught us I wouldn’t be able to apoligise!7

Colourful mineral staining on the the walls of Decco’s Cave

The length of the adit itself is not more than 350m and it consists mainly a two stopes (where mineral ore was excavated) linked by a series of headings (where the parent rock was mined to allow access to the stopes). In many parts the passages are flooded and, similarly to Smuggler’s Cave, there are no signs of the activity of mining, except for a ventilation shaft running from the surface. Curiously, in recent times, an unknown group has developed the mine into an obstacle course, with wooden bridges and a mesh bridge leading throughout it. I can’t say I approve of it. While it shows an insightful continuity of interest in the mine, any such alteration moves the site away from a public amenity to private playground. I prefer, also, to see such mines left as a silent tribute to the forgotten generations of miners who laboured hard and died young, in these places. However, it cannot be denied that considerable skilled effort has been put into this obstacle course and that, in itself, is admirable!

Some of the recent additions to Decco’s Cave

Decco’s Cave has featured prominently in local folklore and indeed Decco, who is generally considered to have been a real character, is but one of the inhabitants of the cave, for it is associated with a number of other colourful characters. One such was an unnamed 19th century hermit. When the hermit’s isolated abode was discovered by a local man, he grew anxious and upset. Learning of the man’s crippled sister, the hermit promised to cure her with a powder, should the man keep his presence secret. When the cure was successfully administered the man returned to thank the hermit; but he also admitted that he had let slip the hermit’s refuge. The hermit issued him with a second ‘cure’ which caused the poor sister to become crippled again and, upon returning to the cave, the man found it entirely empty.8

Another story relates how cave occupant O’Sullivan, the poorest man in Dalkey, was found to have “nothing but gold and silver” in the cave, upon his death!9 While, in yet another tale, it is recounted that a man, taking a shortcut to the sea, passed through the ‘cave’. There he met a strange man and, stooping to tie his shoelace, he noticed the other man’s cloven-hooved foot! He immediately fled from the devil and the cave was sealed.10

The most disturbing, and interesting, of stories returns to the vagrant in the cave. In this story, Decco, the hermit and the devil are all unknowingly blended into one person, named Paddy Reynolds. The story unusually acknowledges that he lived in a former lead mine. Yet more unusual is the introduction of English cave “explorers”. This must surely have some odd connection to the fact that English cavers were active in Ireland at this time. This grim story tells of kids jeering Paddy Reynolds, whereupon:

He got angry with the children. He chased them and caught one. He brought it back to the cave and locked it in a case. All the week men were searching for the body of the child but could not find it. Some explorers came from England and explored the cave. They found the man dead and found the case in which he locked the child and it was dead.11


Lead mining began in nearby Ballycorrus in 1806 and quickly developed through the 1820s, when galena ore was found in large quantities. By the 1850s, an entire mine complex was in successful operation, where smelting houses, mills and lead processing plants were established. Much of the processed lead was used, on-site, to make water pipes and roof flashing, to meet demand for the rapidly expanding city. In 1858, the most obvious architectural feature of the mine, its distinctive lone chimney, with its unique underground flue was built.

The Ballycorus chimney

Despite decades of expansion, however, by the 1860s the mine had become exhausted. The Mining Company of Ireland, who owned Ballycorrus as well as numerous other large working around the country, closed the mine but retained the plant as an industrial centre for smelting; and it even imported ore from abroad. Smelting continued here until the 1910s.

The mine flue at Ballycorus

The most obvious feature remaining today is the chimney which was located at the highest point in the area, over one kilometre uphill from the mine compound. Its location allowed for noxious smelting gasses and smoke to be jettisoned as far away from surrounding farms and villages. Thus, at 26m height, it is sizeable, and can be seen for miles. It is most distinctive for its exposed spiral staircase on the outside of the structure, which is now broken in places to prevent access!

But perhaps of most interest is the chimney flue. This is a very fine underground tunnel which runs 1.4km from the chimney to smelting houses. This huge flue is an ingenious piece of 19th century industrial engineering. Its purpose was essentially to remove pollutants as far away from the community as possible. But it also ‘paid for itself’ in that its length caused refuse gases to cool whereupon lead ‘dustings’ would precipitate onto the walls of the flue. This would then be collected, at great profit. At every 50 yards a set of doors allows access for the purpose of collecting the dustings.12

The mine flue at Ballycorus: limestone, granite and redbrick

The flue itself is constructed predominantly with limestone, but each door segment is re-enforced by large cut granite blocks, The vaulted roof is composed of hand-made redbrick bonded in lime mortar. Today it is home to a particularly large amount of Meta menardi, or European Cave Spiders. These can be spotted hanging from the roof while guarding their distinctive egg sacks.

Meta menardi: The European Cave Spider

These mines constitute Dublin’s role in industrial mining, which never saw a great deal of exploitative work, unlike in the neighbouring county of Wicklow. There are a few small sites, such as at Howth and Clontarf, which were certainly explored for mining potential but these yielded very little ore. There were also extensive lead mines in Dolphin’s Barn, which were abandoned by 1760. The great Dutch illustrator Gabriel Beranger, visited the mines while still in production:

“I descended in these mines in a bucket with a candle in one hand, & holding the cabel with the other, I as obliged to walk bended in the horizontal shafts holding always the candle in one hand and to support my self with the other against the timbers with which the shafts are lined”1

He produced, as ever, a beautiful and atmospheric drawing of the mines, which can be seen here.


While I have covered Dublin’s mines and caves, there remains an additional disjointed category of underground structures and spaces to be explored. As an ancient city and one which saw extremely rapid expansion in the 18th century, Dublin in underlain with many underground vaults, chambers, tunnels and passages. An example of one such structure, which predates the city, is the souterrain. There are many of these scattered throughout the country but few are in Dublin. These were built from the 6th to the 11th centuries, spanning the Early and Middle Medieval ages. They had multiple purposes, including storing of food but were sometimes used for refuge. There are many varieties of souterrain, but they are generally constructed by excavation of underground tunnels which are then banked by drystone walls and lintelled rooves. Often just short tunnels, some feature multiple stories and others, like the example below, boats corbelled chambers.

A corbelled roof chamber in a Dublin souterrain

Interestingly ‘souterrain’, which comes from French, is only recently in use in Ireland. More traditionally they are referred to as caves, and in a sense this is what they are, except they are man-made. The above photo is from Dublin and is not far from the city centre. It features steps down into a short passage which opens into a very large chamber. Within the chamber are multiple air vents and the passage continues but is collapsed.

By far, most underground structures in Dublin relate to the city’s advancement in the 18th century and its industrial growth of the 19th. After the medieval period and with the development of the humble redbrick, the ability to construct large scale underground cellars led to a flurry of pre-Georgian and Georgian era vaulted and barrel cellars. Some of these became quite complex and were often connected by a series of tunnels. The photos below show one such tunnel in Dublin.

A Georgian era tunnel in Dublin

In this time, the historically important but denigrated Poddle river, around which the city grew, was diverted underground via a series of walkable tunnels that lead into the Liffey river.

Similarly the Marino Casino and a demolished manor at Loreto College both have long underground tunnels. The likely purpose of these was to visibly conceal the movement of servants from their masters! This trend did not stop in the 19th century, however, as the University College Dublin campus, which was built in the 1960s, is rumoured to have a series of underground passages. Such passages, it is said, were constructed in response to the 1968 student riots in France; and were built to allow secretive movement of riot police around the campus, should such protests occur in Ireland!

A Georgian era tunnel in Dublin

The subject of such underground features, could easily fill another page, but it is something I hope to return to in detail in the future.

Part I of this article ‘Underground Dublin, Part I: The Caves of Dublin’ is available here.

Deccos’ Cave


1Cowman, D., 2001, ‘The Metal Mines of Dublin City and County, C.1740-1825’ Journal of the Mining Heritage Trust of Ireland, 1, pp. 6166.

2Murray, M., ‘Historical Tradition’, The Schools’ Collection, 0785, p. 217, Duchas.ie. [Available at: https://www.duchas.ie/en/cbes/4498347/4383951 on 07/05/21].

3Clarke, K., ????, ‘Hidden Treasure’, The Schools’ Collection, 0785 p. 176, Duchas.ie. [Available at: https://www.duchas.ie/en/cbes/4498347/4383904 on 19/05/21

4Pratt, G., ????, ‘Story (The Smugglers’ Cave)’, The Schools’ Collection, 0785, p. 95, Duchas.ie. [Available at: https://www.duchas.ie/en/cbes/4498309/4384062 on 07/05/21].

5Barnett, J., 2006, ‘Quarries, Mines and Railways of Dalkey’ Journal of the Mining Heritage Trust of Ireland, 6, pp. 17-21.

6Redmond, M., ????, ‘Decko’s Cave’, The Schools’ Collection, 0796, p. 105, Duchas.ie. [Available at: https://www.duchas.ie/en/cbes/4428225/4387147 on 07/05/21].

7O’Flanagan, F. M., 1942, Glimpses of Old Dalkey, Dublin Historical Record, 4, 2, Old Dublin Society: 1942.

8Mooney, M., ????, ‘The Hermit’, The Schools’ Collection,  0798 p. 125, Duchas.ie. [Available at: https://www.duchas.ie/en/cbes/4428238/4387606 on 27/05/21].

9Dignam, C., ????, ‘Folklore’, The Schools’ Collection,  0798 p. 129, Duchas.ie. [Available at: https://www.duchas.ie/en/cbes/4428238/4387611/4462903 on 27/05/21].

10Young, H., ????, ‘The Devil’s Cave’, The Schools’ Collection, 0798 p. 31, Duchas.ie. [Available at: https://www.duchas.ie/en/cbes/4428238/4387643/4463005 on 27/05/21].

11Dignam, C., ????, ‘Paddy Reynolds Cave’, The Schools’ Collection, 0798 p. 31, Duchas.ie. [Available at: https://www.duchas.ie/en/cbes/4428238/4387808/4462682 on 27/05/21].

12Normoyle, P., 2006, ‘The Ballycorus Leadworks’ Journal of the Mining Heritage Trust of Ireland, 6, pp. 11-16