Inside the Irish ‘hell caves’ where Halloween was born

Go in search of the ancient royal capital that spawned our favourite night of the dead.

By Ronan O’Connell
Published 6 Oct 2021, 15:55 BST
Oweynagat cave
The unassuming entrance to Oweynagat cave, in Rathcroghan, Ireland, belies its central role in Celtic pagan history. It‘s known as a gateway to the demon-filled underworld and the birthplace of the Samhain festival, the ancient roots of Halloween. Now Ireland is pushing for UNESCO World Heritage status for the archaeological site.
Photograph Ronan O'Connell

In the middle of a field in a lesser known part of Ireland is a large mound occupied by sheep. These livestock wander freely, chewing the grass beneath their feet. Yet, had they been in that same location 2,000 years ago, these animals probably would have been stiff with terror, held aloft by chanting, costumed pagans while being sacrificed to Celtic demons that inhabited nearby Oweynagat cave.

Considered by the ancient Celts to be a passage between Ireland and its devil-infested “otherworld,” Oweynagat (pronounced “Oen-na-gat” and meaning “cave of the cats”) was the birthplace of the Samhain festival, the ancient roots of Halloween, according to Irish archaeologist Daniel Curley. Far from the child-friendly event it has become, Halloween can trace its origins to a bloody and eerie ritual marked in Rathcroghan, a former Celtic centre buried beneath the farmland of Ireland’s County Roscommon.

Curley is an expert on Rathcroghan, which was the hub of the ancient Irish kingdom of Connaught. At the heart of Rathcroghan, on that monumental mound, animals were sacrificed at a mighty pagan temple during Samhain. Now Ireland is pushing for UNESCO World Heritage status for Rathcroghan (“Rath-craw-hin”), a 5,500-year-old mystery slowly being decoded by scientists and historians.

The current archaeological site of Rathcroghan displays an artist’s impression of the temple that once stood there. It was the main meeting place of the Connaught kingdom 2,000 years ago.
Photograph by Ronan O'Connell

Rooted in lore

Spread across 2.5 square miles of rich agricultural land, Rathcroghan boasts 240 archaeological sites. They range from burial mounds to ring forts, standing stones, linear earthworks, an Iron Age ritual sanctuary, and Oweynagat, the so-called “gate to hell.”

More than 2,000 years ago, when paganism was the dominant practise among Ireland’s majority Celtic people, it was here in Rathcroghan that the Celtic New Year festival of Samhain (“Sow-in”) was born, Curley says. In the 1800s, the Samhain tradition was brought by Irish immigrants to the United States, where it morphed into the sugar overload that is the American Halloween.

Dorothy Bray, an associate professor and expert in Irish folklore at Canada’s McGill University, explains that pagan Celts divided each year into summer and winter. Within that framework were four festivities. Imbolc, on February 1, was a spring festival that coincided with lambing season. Bealtaine, on May 1, marked the end of winter and involved customs like washing one’s face in dew, plucking the first blooming flowers, and dancing around a decorated tree. August 1 heralded Lughnasadh, a harvest festival dedicated to the god Lugh and presided over by Celtic kings. Then on October 31 came Samhain, when one pastoral year ended and another began.

Rathcroghan was not a town, as Connaught had no proper urban centres, and consisted of scattered rural properties. Instead, it was the kingdom’s meeting place and a key venue for these festivals. During Samhain, in particular, Rathcroghan was a “hive of activity” focused on its elevated temple, which was surrounded by burial grounds for the Connachta elite.

Those same privileged people may have lived at Rathcroghan. The remaining, lower-class Connachta community resided in dispersed farms and descended on the capital only for festivals. At those lively events they traded, feasted, exchanged gifts, played games, arranged marriages, and announced declarations of war or peace.

 (See how people dressed up for All Hallow’s Eve a century ago.)

Festivalgoers also made ritual offerings. Those gifts were directed to the spirits of Ireland’s underworld, says Mike McCarthy, a Rathcroghan tour guide and researcher who has co-authored several publications on this site. That murky, subterranean dimension, also known as Tír na nÓg (“Teer-na-nohg”), was inhabited by Celtic devils, fairies, and leprechauns. During Samhain, some of these demons escaped via Oweynagat cave.

“Samhain was when the invisible wall between the living world and the otherworld disappeared,” McCarthy says. “A whole host of fearsome otherworldly beasts emerged to ravage the surrounding landscape and make it ready for winter.”

Thankful for the agricultural efforts of these spirits, but wary of falling victim to their fury, the Celts protected themselves from physical harm by lighting ritual fires on hilltops and in fields. To avoid being dragged deep into Tír na nÓg by the devils, they disguised themselves as fellow ghouls, McCarthy says. Two millennia later, young children the world over follow this tradition on Halloween.

(These imaginary beasts fuelled nightmares around the world.)

A hillside path leads to Keshcorran Caves in County Sligo, which, according to Irish legend, were gates to hell and connected to Oweynagat.
Photograph by Ronan O'Connell

Despite these engaging legends—and the extensive archaeological site in which they dwell—one easily could drive past Rathcroghan and spot nothing but paddocks. Inhabited for more than 10,000 years, Ireland is so dense with historical remains that many are either largely or entirely unnoticed. Some are hidden beneath the ground, having been abandoned centuries ago and then slowly consumed by nature.

That includes Rathcroghan, which some experts say may be Europe’s largest unexcavated royal complex. Not only has Rathcroghan never been dug up, but it also pre-dates Ireland’s written history. That means scientists must piece together its tale using non-invasive technology and artifacts found in its vicinity.

While Irish people for centuries believed this site was home to Rathcroghan, it wasn’t until the 1990s that a team of Irish researchers used remote sensing technology to reveal its archaeological secrets beneath the ground.

“The beauty of the approach to date at Rathcroghan is that so much has been uncovered without the destruction that comes with excavating upstanding earthwork monuments,” Curley says. “[Now] targeted excavation can be engaged with, which will answer our research questions while limiting the damage inherent with excavation.”

Becoming a UNESCO site

This policy of preserving Rathcroghan’s integrity and authenticity extends to tourism. Despite its significance, Rathcroghan is little known outside of Ireland and attracts few domestic visitors. That may not be the case had it long ago been heavily marketed as the “Birthplace of Halloween,” Curley says. But there is no Halloween signage at Rathcroghan or in Tulsk, the nearest town.

Rathcroghan’s renown should soar, however, if Ireland is successful in its push to make it a UNESCO World Heritage site. The Irish Government has included Rathcroghan as part of the “Royal Sites of Ireland,” which is on its newest list of locations to be considered for prized World Heritage status. The global exposure potentially offered by UNESCO branding would likely attract many more visitors to Rathcroghan.

But it seems unlikely this historic jewel will be re-packaged as a kitschy Halloween tourist attraction. “If Rathcroghan got a UNESCO listing and that attracted more attention here that would be great, because it might result in more funding to look after the site,” Curley says. “But we want sustainable tourism, not a rush of gimmicky Halloween tourism.”

Those travellers who do seek out Rathcroghan might have trouble finding its hell cave. Oweynagat is elusive—despite being the birthplace of Medb, perhaps the most famous queen in Irish history, 2,000 years ago. It is barely signposted and hidden beneath trees in a waterlogged paddock at the end of a one-way, dead-end road, about a thousand yards south of the much more accessible temple mound.

Visitors are free to hop a fence, walk through a field, and descend into the narrow passage of Oweynagat. In Ireland’s Iron Age, this behaviour would have been enormously risky during Samhain, when even wearing a ghastly disguise may not have spared the wrath of a devil.

Whether dodging demons or going house-to-house, for the ancient Celts and today’s kids alike, October 31 is a high-stakes operation. There is one key difference. Two millennia ago, the ghouls that marauded on Samhain were gifted animal carcasses.

Nowadays, the youthful mobs that roam on Halloween are appeased with sweets. As they indulge in this annual frolic, most trick-or-treaters won’t realise they’re mimicking a prehistoric tradition linked to hell caves, supernatural beasts, and a buried Celtic kingdom.

Ronan O’Connell is an Australian freelance journalist and photographer based between Ireland and Thailand.

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