Subscribe for Unlimited Access to Turtle’s History Quarter.

Includes content from Vanishing Ireland, Easter Dawn, Dublin Docklands, The Irish Pub, Maxol and many more, as well as Waterways Ireland, the Past Tracks project and hundreds of historical articles on Irish families, houses, companies and events.

The Secrets of Dublin’s Underground

The junction between the Poddle tunnel and the Liffey is visible at low tide.

On 3 August 2012, two men were reported to have vanished down a manhole beside Dublin Castle sending social media sites into a state of theoretical dementia. What could this subterranean pair have been at? Were they a Guy Fawkes re-enactment group seeking to blow up the Central Bank? Were they historians tracking the escape routes of beleaguered Catholic priests during the Penal Times? Were they plotting a major robbery? Or were they just shooting a Carlsberg commercial?

The underground of any city is replete with the possibilities of another world. Think of the darkly magical catacombs of Edinburgh or Rome, or the ghostly caverns of the Royal Mail’s abandoned Tube lines under London.

Alas, most of the legends abounding of a subterranean Dublin riddled with interconnecting tunnels are codology. The main problem is that our capital city is too wet for a decent underground. Much of the ground beneath the city rests upon a huge soggy swathe of reclaimed marshland.




Take Ship Street, for instance, or ‘Sheep Street’ (Sráid na gCaorach) as it was originally known, thanks Cóilín Ó Cearbhaill. This is the street that hosts the manhole down which the two curious men disappeared. This street rides directly above the River Poddle, one of over a hundred forgotten streams and watercourses running beneath the capital city. The waters of the Poddle rush down from the Dublin Mountains through Tallaght and Greenhills and then swirl into the city centre.

Transport yourself back to Viking Dublin and you’d find a small, bustling town right where the Poddle met the Liffey, in an area now roughly bound by Essex Street in Temple Bar and Dublin Castle. The river culminated in a black pool – the ‘dubh linn’ that gives the city its name – in the present-day castle gardens.

In the late 12th century, skilled Anglo-Norman artisans borrowed a chunk of the river to feed a moat that ran around the original Dublin Castle. Four hundred years later, the rebel chieftains Red Hugh O’Donnell and Art O’Neill escaped from the castle by slipping out a drain into the moat and then onwards out the Poddle. The junction where the Poddle met the moat was discovered during castle renovations in the 1980s.

At some point, the Poddle became better known as the River Salach, meaning ‘dirty river’ in Irish. Presumably the water was not looking the purest after numerous centuries of medieval sewage. The river was deftly bricked over by the Victorians, a project completed in 1902, and banished to the underworld, constrained in its redbrick prison.

You can hear the river gushing and slurping beneath the city, right where that manhole lies. Bring a stethoscope to the castle and listen to the pavements. The water flows through Ship Street Gate into the castle’s Lower Yard. It then bifurcates at the Palace Street Gate, with one line running off beneath the Olympia Theatre and Essex Street into Temple Bar where it is rejoined by the other line around the back of The Purty Kitchen (formerly Bad Bobs).

And if you’d like to see this poor, unloved river finally escaping into the Liffey, cross over the Halfpenny Bridge at low-tide and look out for the metal grid on the waterfront of Wellington Quay, directly below the Clarence Hotel.

The Manhole Men were foolhardy to enter the Poddle tunnel given the summer we’ve had. The water level within can rise so suddenly that, if you’re caught down there, you wouldn’t stand a chance. And when a flood is on, the river erupts, gobbling up the gardens and cellars innocuously built along its course.

It seems likely the Manhole Men were attempting to pull off a bank heist. In 1985, robbers attempted to break into AIB’s bank vaults on Dame Street by tunnelling underground from a derelict building by the castle. They broke though to the Poddle tunnel, located the vaults and began chiselling. However, the ambitious attempt was foiled by what was then a cutting edge sensory alarm and the thieves scarpered without a penny.




The Front Square, or Parliament Square, at Trinity College Dublin.

Away from the Poddle, there are a few places where the Dublin underworld exists. One of the most talked about is at Trinity College in Dublin, which features in the accompanying photograph. I’d have used a good photo of Dublin underground instead if I had found one but all the ones I found were rather too dark and vague – if you have any good ones, please feel free to post them, with captions, at Wistorical.

Given that the 420-year-old college was built upon a monastery devoted to the pagan riddled world of All Hallows, it’s not surprising that its students are wont to speculate about an eerie underworld beneath the cobbles. After all, it is not so long ago that engineers installing a water pipe near the college’s Campanile stumbled across twenty bodies and a camel bone.

Unfortunately, the underground tunnels at Trinity are all rather more bookish than ghoulish. The best known connects the majestic Long Room Library to the octagonal War Memorial Reading Room at Front Square and was completed in 1937. Access is limited to staff only, although students can clamber down an endless stairway that leads to a subterranean walkway linking the Berkeley Library to the Lecky Library and the Early Printed Books department.

There are also said to be tunnels from the Provost’s House, and from Front Square across the street to Parliament House on College Green. It’s hard to know how much of this is mythology or not. Some minds run riot in snowy times when a long strip of cobbles running through Front Square starts to thaw quicker than anywhere else. Sadly, that is simply the consequence of a large heating duct running between the Examination Hall and the Chapel.

One reason why Trinity is thought to have more tunnels than it actually does is because of all the wine cellars built beneath the houses in Front Square. The largest of these sprawls under House 10 and is similar in style to the college’s Buttery Bar. Access is not surprisingly restricted, particularly since a short-lived era in which the merry students living in House 10 worked out a way to get down to the cellars.[i]




One underground gem that has lately come to light again is the 1600 year old St. Patrick’s Well that lies beneath the pavements of Nassau Street. This ancient pilgrimage site is said to have been blessed by St Patrick himself.

The street used to be called both Nassau Street and Sráid Thobar Phádraig (Patrick’s Well Street). However, on 13th June 2013, Dublin City Council officially changed the name to Nassau Street / Sráid Nassau. It seems a pity to remove such a historic references to the well. The well itself is also in danger of being sacrificed to make way for a Luas Cross City construction project to link the Red and Green lines although the Railway Procurement Agency insists the ancient site will not be affected by the proposed works.

The underground well, which remains closed to the public, is about four feet underground and lies behind a crumbling locked gate. In its original state, it is thought to have been nearly 40 feet deep. For more, see Gearóid Ó Branagáin’s excellent Ancient Wells of Ireland Facebook group.




The Guinness tunnel.

The Guinness brewery has an 864 ft spiral tunnel running under St. James’s Street. This was built in the 1870s to enable locomotives to travel between the brewery’s upper and lower levels and is similar in design to the tunnels running through the Alps. A passenger tunnel, constructed in 1895, runs parallel to the railway tunnel and is now a pedestrian walkway linking the two parts of the brewery. Pedestrians also have limited access to a 370-foot long bolted-steel tunnel, constructed in 1947/48, to transfer steam from the Power House to production areas across the brewery site.

In fact, most of Dublin’s underground “tunnels” have perfectly rational functions. Most are service routes, designed to bring pipes and cables from one place to another. Others aren’t even tunnels at all but short passageways and storage rooms.

The ‘tunnels’ that reputedly lie beneath Dublin’s Georgian squares – Merrion, Fitzwilliam, St. Stephen’s Green and such like – were simply basements that extended out under the street to incorporate coal bunkers. Hence, all the cast iron coal covers you can see on the pavements.

There are said to be a number of Second World War air-raid shelters under the city. One is beside the Parnell monument in the middle of O’Connell Street. Another is reputedly at Ballybough and connects to Laurence O’Toole’s church in East Wall, and there is another below Fr. Matthew Square, off Church street. Perhaps the most visible is the one that now lies beneath the grassy mound at the Fitzwilliam Street Lower corner of Merrion Square Park.

And, as Cormac Lowth advised me, there is also a tunnel under the Liffey at Ringsend which takes water and electrical pipes under the river. It starts at the small blockhouse beside the St Patrick Rowing Club, where it can be accessed by a ladder, and can be entered again on the North Wall extension. It is about two metres in diameter.




There were undoubtedly some tunnels that were specifically designed for secrecy, such as the passageway that reputedly ran from the Custom House to the notorious brothels of the Monto, now Foley Street, and the tunnel connecting the Bridewell with the Four Courts.

In 1909, Britain’s Royal Engineers built a tunnel connecting St Brican’s Military Hospital, via Arbour Hill Prison (formerly the military prison), to the former Collins Barracks.

A similar desire for discretion inspired the underground passageway emanating from the former Guinness family home at Farmleigh in Phoenix Park. This enabled household servants to come and go without intruding upon the aesthetic view of the well-to-do residents within.

A tunnel in front of St. Anne’s Park in Raheny likewise ensured people could use a right of way to Clontarf without disrupting the gentry’s view to the sea. There is also a tunnel that reputedly connects the Casino in Marino to Lord Charlemont’s house.

Tunnelling your way into enemy territory was a concept popularized by the unfortunate souls who dug the trenches in World War One. During the Irish Civil War, rumours that the Irregulars were digging a tunnel from a house on Merrion Row to the foundations of the government buildings at Leinster House prompted a massive swoop by a combined force from the Criminal Investigation Department and the Irish Army. They spent two hours searching the basements and cellars of every house on the street but found nothing.[ii]




Dublin’s churches yield the occasional underground gem, such as the solemn catacombs of Christchurch Cathedral or the 13.7 metre long brick-vaulted tunnel that runs along an ancient right-of-way beside St Audoen’s Church on High Street. Contrary to many hopes, there’s no sign of any that were used as torture chambers by the Knights Templar.

That said, a few screams have probably been emitted in the stone tunnel of St. Michan’s, lined as it is with vaults full of open coffins and mummified corpses.[iii]

And spare a thought for Scaldbrother. According to the 16th century historian Richard Stanihurst, this infamous scoundrel lived in a large rambling cave that ran beneath present-day Smithfield market (then Oxmantown Green). His flourishing livelihood was achieved by suddenly popping out from his cave, snatching possessions from the first people he came across and legging it back down again. “The varlet was so swift of foot as has oftsoon outrun the swiftest and lustiest young men of Osmanstown”. Eventually he was caught and hanged.[iv]

Public desire for a secret underworld shows no signs of abating as per the ongoing story of a furtive tunnel beneath the new Criminal Courts of Justice. “The famous underground tunnel that doesn’t exist!”, said Peter McGovern, the architect who designed the building. “The mythical tunnel! There are certainly a number of ways in and out of the building but, for the budget we had, there’s no tunnel.”



With thanks to Pat Liddy, Eibhlin Roche (Guinness Archives), Patricia Parfrey (Parish Administrator, St. Michan’s), Emmeline Henderson (Irish Georgian Society), Tommy Graham (History Ireland), Dave Walsh, Máirtín D’Alton, Oriel JeinDevlin, William Rowan Hamilton, Shane MacThomais (Glasnevin Trust) and Alan Breen (



[i] A smaller cellar can be found under the Dining Hall steps and offered convenient proximity to the Commons.

[ii] Weekly Irish Times, Saturday, February 17, 1923, p. 4

[iii] If you’re at the Boars Head pub on Capel Street, stroll uphill a little to Meetinghouse Lane and you can look down at St. Mary’s Abbey and see the original Chapter House, now largely buried seven foot underground.

[iv] A chronicler from 1845 described how builders digging foundations for a house often broke through into this extended cave while some parts were used by Smithfield’s brewers for storing ale. (Hidden Dublin: Deadbeats, Dossers and Decent Skins, p. 215, by Frank Hopkins

Other rumoured tunnels include:
* Kilmainham Jail to St Michael’s CBS (Richmond Barracks) Inchicore.
* The Freemasons’ Hall on Molesworth Street (or possibly Buswell’s Hotel) to Leinster House.
* Terenure College Lake to Bushy Park House.

The biggest Victorian tunnel in the city is the 750 metre long Phoenix Park tunnel which, built in 1875, connects Heuston Station to Connolly Station via the Liffey Railway Bridge and is mainly used for freight trains. For more on that, see

A mysterious red-brick tunnel at Coke Lane, 2.5m in height and 1.25m in width, with plastered wall and a flat stone floor. The tunnel was comparable to other examples, mainly of 18th-century date. Though it was found close to the river inlet prior to the 18th century, it did not look like a drain or sewer nor did it contain the sort of silt stratigraphy which would be expected if this were the case. Its flat floor would suggest it was intended as some sort of access route. It was, however, puzzling, as there is no large house or estate in line with it. It is possible that it was used as an access to the river at some stage.