When it comes to hidden ways beneath the Emerald Isle, the top 10 secret tunnels and passageways reveal a wild mix of crime, royalty, and rebellion that will make you wonder what else lies below the streets.
10 When You Gotta Go
Back in 1985 a bold crew of thieves decided the fastest way to loot Dublin’s Allied Irish Bank on Dame Street was to tunnel straight through the earth. Their plan went sideways when they emerged not into the vault but into a ladies’ restroom, triggering an alarm that blew their cover.
The operation kicked off just outside Dublin Castle, a stone’s throw from the city’s main police communications hub. They began digging on the Thursday before Easter and, after a frantic sprint of underground work, surfaced on Easter Monday.
The gang managed to carve out a 23‑metre (about 75‑foot) shaft that punched straight through to the bank’s outer wall. Unfortunately, the accidental pit‑stop in the restroom set off a warning system that alerted the police during the long holiday weekend.
Faced with a swift police response, the robbers fled empty‑handed. Even if they had succeeded, the vault reportedly held only about $147,000, and bank officials doubted the thieves could breach the reinforced strong‑room where the cash was stored.
Top 10 Secret Tunnel Tales
9 Staircase Tunnel Discovered In Cork After 230 Years
Spike Island, once a grim prison and defensive outpost in Cork Harbour, now draws tourists with its layered history. From a seventh‑century monastic settlement to a bustling 1600s smuggling hub, the island has seen many lives.
The first artillery fort sprang up in 1779, a direct response to the American Revolutionary War, and the island later served as a British supply base for forces bound for North America and the West Indies. By 1790, the Irish Board of Ordnance erected a permanent fortification.
In August 2020, a wall that had sealed off a hidden corridor for generations was finally removed, unveiling a tunnel that snakes beneath the fort’s walls – a classic “sally port” used for quick exits under fire.
A sally port is essentially a small, fortified doorway that allows troops to dash out while staying protected from enemy fire. It’s a tactical shortcut, often guarded by sturdy doors or walls.
When staff pried open the entrance, they discovered a spiralling staircase that seemed to float out of a Harry Potter illustration, adding a magical twist to the gritty military past.
The newly uncovered passage now leads from the inner fort straight out to the surrounding moat. A second fort erected in the early 1800s likely rendered the tunnel redundant, which explains why it was sealed and forgotten for over two centuries.
8 Frescati Stream
Buried beneath the former grounds of Frescati House, a 1739 estate once home to the Trinity College provost’s family, lay a clandestine tunnel. Emily FitzGerald, Duchess of Leinster, later commissioned the passage to channel seawater straight to the manor, though the route is now sealed and its exact coordinates remain a mystery.
When the house was demolished in the twentieth century, the land transformed into a bustling shopping centre. Yet the Frescati Stream – also known as the Priory Stream – still threads its way beneath the car park, weaving past apartments, slipping under the main road, and finally surfacing in Blackrock Park.
Historically, locals may have used this hidden watercourse to slip away from Crown Militia raids originating at Dublin Castle, offering a discreet escape route for those under siege.
7 The Goggins Hill Tunnel
Since its closure in 1961, the Goggins Hill Tunnel – sometimes spelled Gogginshill – has held the title of Ireland’s longest forsaken passage, stretching an impressive 828 metres (about 2,717 feet). Originally cut for railway traffic, the tunnel was hewn by a crew of 300 men beneath the village of Ballinhassig between 1850 and 1851.
Today the tunnel is choked with overgrowth, giving it an eerie, underworld vibe. It boasts three ventilation shafts, and while some sections remain raw rock, others have been reinforced with brick linings to stave off collapse.
Prospective explorers should note that the tunnel sits on private property. Permission from the landowner is mandatory; trespassers are not welcome, though those who obtain consent can venture inside under guided conditions.
6 The Ballymore Tunnel, County Kildare, And Casino Marino, Dublin
In 1852, Lady Isabella Tasca Stewart‑Bam of the Ards estate commissioned the Ballymore tunnel so she could slip to church without the prying eyes of nearby peasants, creating a discreet subterranean walkway for the aristocracy.
Across Dublin, the Casino Marino complex housed its own secret network. Built in the eighteenth century as a pleasure house for James Caulfeild, 1st Earl of Charlemont, the Casino featured eight concealed passages that linked the main house to its gardens, allowing servants to move unseen and preserve the estate’s immaculate vistas.
Legend has it that the Earl imagined extending these tunnels all the way to the sea, but his untimely death and depleted coffers halted the grand scheme, leaving the purpose of many shafts shrouded in mystery.
Fast forward to 2016, when hidden corridors beneath the Casino Marino grounds were finally opened to the public. These passageways later served as testing chambers for Michael Collins and fellow Irish revolutionaries, who used them to fire sub‑machine guns during the War of Independence.
5 1,000‑Year‑Old Souterrain Discovered In County Cork
In 2015, road‑widening crews in the Caha Mountains of County Cork stumbled upon a remarkable find: a souterrain hewn through solid rock, dating back roughly a millennium. The term “souterrain” derives from the French “sous‑terrain,” meaning “underground passage.”
Archaeologists believe the concept of souterrains travelled to Ireland from Gaul during the late Iron Age. These hidden chambers are typically linked to settlements and are frequently discovered near ancient ringforts.
The Bonane workers uncovered the tunnel while expanding a tourist route, shedding new light on an area previously overlooked by archaeologists despite known Neolithic activity in the surrounding mountains.
4 Sinkhole In Dublin Reveals Brothel Tunnel For Politicians
In 2015 a sudden sinkhole yawned open on Dame Street, a major Dublin thoroughfare that leads toward Trinity College and Christ Church Cathedral. The 1.8‑metre‑deep (about six‑foot) void collapsed into an ancient cellar hidden beneath the road.
Historian Gerry Cooley suggests that, in the nineteenth century, Irish politicians used a concealed tunnel to slip into nearby brothels. The uncovered cellar likely formed part of that clandestine route, remaining in use until the former Irish Parliament House was repurposed as the Bank of Ireland after the 1800 Act of Union.
3 Underground Jail Cells
During renovations at a secondary school in Trim, County Meath, workers ripped down a wall to discover a series of intact jail cells hidden in underground tunnels beneath the building.
The school sits near the site of the former Trim Gaol, demolished in the 1950s. Originally, the industrial school aimed to keep pauper children out of workhouses by teaching them trades. The location is also linked to eerie events: a teacher was murdered in the schoolyard in 1912, and forty years later, two men died when a wall collapsed while they were placing explosives to demolish the old jail.
2 River Poddle
The River Poddle snakes beneath Dublin Castle, winding its way through the city centre before emptying into the River Liffey at Wellington Quay. Manhole covers offer access to its hidden channels, inviting the daring to drop in and explore.
In 2012, two men in waterproof gear and gloves were captured on CCTV near Dublin Castle, apparently slipping into a manhole to investigate the Poddle’s depths. The Garda sub‑aqua unit launched a search, but the pair vanished despite their voices echoing when the cover was lifted. Some speculate they were urban explorers; others suspect they were hunting for treasure, given the tunnel’s proximity to the Assay Office’s gold and silver vaults and a passage beneath the Central Bank on Dame Street.
1 The Streets Under Limerick
When Limerick renamed its streets in the early twentieth century after the Irish Free State’s birth, each new name hid a secret: beneath the surface lay the original English‑named sewers. For example, today’s O’Connell Street sits directly above the old George’s Street, once named for King George III.
It’s rumored that, in the past, one could walk the entire city underground from one side to the other. However, many of those tunnels have been sealed with concrete, leaving only a handful still accessible. Holes in the tunnel ceilings reveal where coal was once delivered into bunkers beneath the streets, and the network, originally linked to sewers, was used to drain rainwater – an admittedly unpleasant trek for anyone brave enough to venture below.