Watch: Treasure hunt leads documentary makers to Kilkenny's Knockroe passage tomb

Knockroe passage tomb in South Kilkenny will feature in a new TG4 documentary that airs this December 20 at 9.30pm.

Rún na Bóinne sees journalist and folklorist Seán Mac an tSíthigh and a team of leading international scientists undertake a quest to uncover the location of a long suspected second chamber at Newgrange, Meath. And the treasure hunt leads documentary makers to Knockroe in Kilkenny.

During excavations in the 1960s, the Boyne Valley began to give up some secrets. The winter solstice alignment at Newgrange was rediscovered and the cairn’s highly decorated kerbstones revealed. When the monument was dated at over 5,200 years old - older than the Egyptian pyramids and Stonehenge - the map of the ancient world was turned upside down. But incredibly, Newgrange was never fully excavated; the vast majority of this ancient structure remained untouched and its secrets intact. Yet in the decades since, rumours persisted of a second as yet undiscovered chamber.

In Rún na Bóinne [Secret of the Boyne], award winning journalist and folklorist Seán Mac an tSíthigh seeks clues to this mystery scattered across time and across the Irish landscape.

He revisits the remarkable finds of the 1960s excavations in the Boyne Valley to tell a new story carved into our most well known yet mysterious monument. And in an Irish TV first, the filmmaker behind this documentary Neal Boyle has brought leading scientists from Ireland and across Europe, and cutting-edge technology, to join Seán’s quest to locate the second chamber. 

Newgrange is unlikely to be extensively excavated in the foreseeable future. It’s an invasive, time consuming and expensive process.  But new, non-invasive technologies like micro gravity survey and geo-radar scans now offer the possibility of a tantalising glimpse into the deep, ancient heart of the monument.

So Seán is joined by scientists, including Mayo based archaeological geophysicist Kevin Barton and Slovakian geophysicist Roman Pasteka and his team of experts. As they embark on a tight, nine-day survey of the mound, Seán attempts to narrow their search as he traces the clues that have led to the belief a second chamber may exist.

Newgrange is the jewel in, and pinnacle of the Boyne Valley Neolithic complex. We’re told the ancient Irish built these vast complexes as tombs or ceremonial burial sites for an elite. But as Seán’s investigation reveals, passages and chambers in Newgrange’s sister monuments Knowth and Dowth are also constructed to capture alignments to key dates. Could a second chamber at Newgrange also target a celestial event and if so, are these monuments much more than passage graves?

And that brings the film crew two hundred kilometres south of Newgrange to County Kilkenny.  On slopes above the Lingaun River, lie the skeletal, neolithic remains of Knockroe. Like the Boyne valley monuments, it was built around 5000 years ago. And it was here during excavations in the 1990s that archaeologist Prof Muiris O’Sullivan and his team made an exciting discovery. Although smaller, Knockroe is remarkably similar to Newgrange as it aligns to the winter solstice rising sun. But it also contains a second chamber aligned to the winter solstice setting sun. 

“Knockroe is great in that you can clearly see the cairns stones exposed in the landscape,” says Neal Boyle, the director and producer of the documentary.

“It’s like the open mechanism of an ancient watch or clock and we can see how it worked.  When you think about how the builders had to observe and track the sun over extended periods of time in order to design these alignments into the cairns, you start to think about our ancestors in a different way. But does Knockroe give us a clue as to where we should look for a second chamber at Newgrange?”

Seeking answers in ancient manuscripts, the landscape, folklore and the art, Rún na Bóinne decodes the stones and stories. Deciphering the mechanics of this architecture, the documentary traces the development and innovation of these ancient builders across Ireland from west to east, to offer a portrait of star-gazing ancestors mapping their first intellectual steps into our very landscape. But will the rumours be proved true; will ancient clues and modern science locate a second chamber?  Or will the mound keep its secrets?  Either way, this documentary promises to rewrite the story of Newgrange and its builders in our imaginations.  

Rún na Bóinne airs on TG4 Wednesday December 20 at 9.30pm. It will be repeated on December 23 at 11.35pm.