As the sun breaks the horizon this morning at 8.38 a.m., a cluster of people will huddle from the cold and repeat a ritual first practised 5,000 years ago. They will watch as the first light of the winter solstice pierces to the centre of the passage grave at Newgrange.
This year's celebrities to witness the event include the Minister for Arts, Heritage, Gaeltacht and the Islands, Ms de Valera, and her guest, the Northern Ireland Minister of the Environment, Mr Roy Foster.
Weather permitting, they will see sunlight creep slowly along the 19-metre stone passage, which was built 500 years before the great pyramids at Giza.
It will be a quiet event compared to last year's hoopla when RTE television and radio crews attempted to bring the drama of Newgrange to a wider audience. Things didn't quite work out however, proving that, like a roller-coaster, you have to be there to really experience it.
The usual fixation with the solstice and the dawn sunlight tends to diminish our appreciation of what the builders of Newgrange, and the nearby passage graves at Dowth and Knowth, actually accomplished.
However, Ms Clare Tuffy, manager of the Bru na Boinne visitor centre, is in no doubt about the remarkable nature of the feat. Newgrange has astronomical significance as the oldest known structure with an obvious solar alignment, but it is also a remarkable architectural and engineering achievement, she explained.
Passage graves are made by building the stone tunnel and chambers first. Then huge amounts of stone, soil or both are heaped up to form a mound or cairn above the stone works, leaving them "underground".
The graves were built without technology and would have demanded an enormous amount of labour. The Newgrange cairn is drum-shaped and measures 80 metres across, Ms Tuffy said. Its builders heaped an estimated 200,000 tonnes of small stones 13 metres high above the passage and inner chamber.
"Most of this stone would have been brought from the terraces of the River Boyne," she said. "There is a 20-minute walk between the cairn and the river bank and even empty handed it is a challenge."
The three passage graves were built about 5,000 years ago, one assumes by local farmers who lived along the Boyne. Archaeologists have found evidence that these early farmers had tilled the river valley's rich soil for at least 1,000 years before construction began, Ms Tuffy explained. "They must have been a wealthy community to let the people out of the fields to build these monuments."
Dowth was the first to be built, followed by Newgrange and finally Knowth. The engineers and architects who built Knowth had learned a great deal and greatly improved their building skills, she said. They clearly were full-time "experts" who knew what they were doing.
Newgrange has the finest astronomical alignment, pointed east towards the dawn winter solstice sun. Knowth is not so tightly aligned but is much more complex, Ms Tuffy explained.
The Knowth cairn is more rounded and is only 10 metres deep but there are two separate passages and chambers, one facing east and one west. The back-to-back chambers are just three metres apart and the tunnels are much longer than the 19 metre run at Newgrange. Knowth's western passage is 34 metres and its eastern is 40 metres. "They may have built Knowth as a focal point for celebrations in spring and autumn," Ms Tuffy said.
Prof George Eogan, former professor of archaeology at University College Dublin, has been excavating and studying the passage graves since 1962 and his work has revealed many secrets, Ms Tuffy said. "They would have been built by the same culture but they are not linked as some would have hoped."
They are described as graves but they likely served many purposes, given the effort involved in building them. "They were far more than simply places to put the dead."
They could have been used to honour dead ancestors and may have been used to mark out territory, she suggested. They were also important indicators of status and power.
The Celts were not the authors of these structures, she added. They were built long before the Celt culture began to have an influence on Ireland, some time around 500 B.C. "These people were not Celtic. They lived as long before the Celts as the Celts did before us."
Newgrange is open to the public seven days a week all year and the full Knowth site will open for visits by May 2001. All visits to the passage graves begin at the Bru na Boinne centre, west of Drogheda, from where visitors will be brought to the passage graves. Ms Tuffy recommends that visitors arrive early as only 600 people can be accommodated at Newgrange in any one day and late-comers won't be able to enter the passage and chamber.