About 100 people gathered at the country's most southerly Neolithic passage tomb at Knockroe near the village of Windgap, southwest Co Kilkenny, for yesterday's winter solstice.
But despite clear skies, the sunset did not "light up" the 5,000-year-old burial chamber to great disappointment.
However, the reason, according to Dr Muiris O'Sullivan, head of the school of archaeology at UCD, is simply that "the tomb's roof stones have fallen off" exposing the chamber to daylight and that "modern ditches and sheds" also hide the effect. However, in its original state, he said the chamber "would be illuminated like Newgrange".
Dr O'Sullivan, who is leading excavations at the site in a valley close to the Tipperary border, described Knockroe, which was only discovered in the late 1980s, as "the Newgrange of the south".
He added that the passage tomb, known locally as "the Caiseal" is the only one in the country with separate tombs facing east and west so that one illuminated at sunrise and the other at sunset. Newgrange is only illuminated at sunrise.
He has been excavating the site "which is better known in Europe than in Dublin" for the past 15 years and believes that it is "one of the most important archaeological sites in Ireland". The roof stones have been found although a decision has yet to be made about "restoring" the passage tomb. The artwork visible on a number of stones is "very important" and Knockroe is one of a small number of decorated sites outside Meath.
Tom Morrissey, the farmer who owned the land "before it was taken over by the OPW", said yesterday the site had traditionally been known as "the Druid's Altar" and was "treated as a spooky place".
His neighbour, Noel Dunphy, said "it wasn't a place you would want to be after dark".
In local folklore, people with the surnames carrying the prefix "O", "Mc" or "Mac" were subjected to the howls of a banshee when passing the spot. Michael Egan, a local village historian who attended the gathering, said those sounds were most likely made by "a barking fox".
The passage tomb had been completely obscured by undergrowth and surrounded by trees when a local man, the late Johnny Meagher, "noticed carvings on the stone illuminated by the sun one evening after a shower of rain".
The nearby village of Ahenny is also famous for its 9th-century High Crosses.