A small cave seen in a grassy land

Inside the Irish ‘hell caves’ where Halloween was born

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

The unassuming entrance to Oweynagat cave, in Rathcroghan, Ireland, belies its central role in ancient Irish history. It‘s known as a gateway to the demon-filled underworld and the birthplace of the Samhain festival, the traditional 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 where sheep wander and graze freely. Had they been in that same location centuries ago, these animals might have been stiff with terror, held aloft by chanting, costumed celebrants while being sacrificed to demonic spirits that were said to inhabit nearby Oweynagat cave.

This monumental mound lay at the heart of Rathcroghan, the hub of the ancient Irish kingdom of Connaught. The former Iron Age center is now largely buried beneath the farmland of County Roscommon. Ireland is currently pushing for UNESCO World Heritage status for Rathcroghan (Rath-craw-hin). 

Rooted in lore

Spread across more than two square miles of rich agricultural land, Rathcroghan encompasses 240 archaeological sites, dating back 5,500 years. They include burial mounds, ring forts (settlement sites), standing stones, linear earthworks, an Iron Age ritual sanctuary—and Oweynagat, the so-called gate to hell.

More than 2,000 years ago, when Ireland’s communities seem to have worshipped nature and the land itself, it was here at Rathcroghan that the Irish New Year festival of Samhain (SOW-in) was born, says archaeologist and Rathcroghan expert Daniel Curley. In the 1800s, the Samhain tradition was brought by Irish immigrants to the United States, where it morphed into the sugar overload that is American Halloween.

Dorothy Ann Bray, a retired associate professor at McGill University and an expert in Irish folklore, explains that pre-Christian Irish divided each year into summer and winter. Within that framework were four festivities. Imbolc, on February 1, was a 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 Irish 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 centers and consisted of scattered rural properties. Instead, it was a royal settlement 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 communities resided in dispersed farms and descended on the site 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 may have made ritual offerings, possibly directed to the spirits of Ireland’s otherworld. That murky, subterranean dimension, also known as Tír na nÓg (Teer-na-nohg), was inhabited by Ireland’s immortals, as well as a myriad of beasts, demons, and monsters. During Samhain, some of these creatures escaped via Oweynagat cave (pronounced “Oen-na-gat” and meaning “cave of the cats”).

“Samhain was when the invisible wall between the living world and the otherworld disappeared,” says Mike McCarthy, a Rathcroghan tour guide and researcher who has co-authored several publications on the site. “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 people protected themselves from physical harm by lighting ritual fires on hilltops and in fields. They disguised themselves as fellow ghouls, McCarthy says, so as not to be dragged into the otherworld via the cave. 

(These imaginary beasts fueled nightmares around the world.)

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 it never been dug up, but it also predates 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 knew 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 one of Ireland’s less frequented attractions, drawing some 22,000 visitors a year compared with more than a million at the Cliffs of Moher. 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 travelers who do seek out Rathcroghan might have trouble finding Oweynagat cave. Oweynagat is elusive—despite being the birthplace of Medb, perhaps the most famous queen in Irish history, 2,000 years ago. Barely signposted, it’s hidden beneath trees in a paddock at the end of a one-way, dead-end farm track, about a thousand yards south of the much more accessible temple mound.

Visitors are free to hop a fence, walk through a field, and peer into the narrow passage of Oweynagat. In Ireland’s Iron Age, such behavior would have been enormously risky during Samhain, when even wearing a ghastly disguise might not have spared the wrath of a malevolent creature.

(The twisted transatlantic tale of American jack-o’-lanterns.)

Two millennia later, most costumed trick-or-treaters on Halloween won’t realize they’re mimicking a prehistoric tradition—one with much higher stakes than the pursuit of candy. 

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

A version of this story appears in the October 2022 issue of National Geographic magazine.

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