Around 2,000 people have gathered at Newgrange to celebrate the Winter Solstice.
The ancient passage tomb is aligned for the rising sun on the shortest day of the year to shine into the inner chamber.
The sky was mostly clear but cloud on the eastern horizon obscured the sunrise. It has since cleared and people are now queuing to get into the inner chamber.
Just 14 people get the rare privilege of being inside the chamber for sunrise on the shortest day of the year.
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They are two guides and six winners of the free solstice lottery and their companions.
Several of this year's winners live overseas but one is based in Balbriggan, Dublin.
This year's winter solstice, the exact time when the sun reached its lowest point in the Northern Hemisphere sky, is 3.03pm.
Celebrations at Brú no Bóinne will continue this evening at Dowth where the passage tomb is aligned with the solstice sunset.
Watch: 'I think it's a very spiritual place' - Crowds gather for Winter Solstice at Newgrange
Newgrange Lottery winners speak of awe at witnessing Winter Solstice
Newgrange Lottery winners have spoken of their awe at being in the inner chamber of the monument at sunrise on the shortest day of the year.
Six people who entered the free lottery to be in the ancient passage tomb in Co Meath won a pair of tickets each to witness the moment when the rising Winter solstice sun enters the chamber through lightbox.
Clouds low on the eastern horizon obscured the sun as it rose but Rory McKenna who travelled from his home in nearby Balbriggan said enough light still entered the chamber.
"You could see the effect of it there. You know...it was good, because you definitely could see all the light doing what it was supposed to do," Mr McKenna said.
Jimmy Hennessy had come from New York with his daughter, Molly. He had entered the lottery after a visit to Newgrange captured her imagination.
Molly Hennessy said she thinks she has read every book on Newgrange, "the first time we were here was about a year ago in January, and it was incredible".
"It was quiet. There was really nobody here. It was really lovely. And, I mean, I just kind of became obsessed with it.
"I'm an archeology major, so I just thought it was the coolest thing. And so he started entering the raffle, and we got lucky, and we're here. And it was just..it was really incredible," Ms Hennessy said.
Jimmy Hennessy's grandfather emigrated from Co Laois about a century ago.
He said he has always felt a deep connection to Ireland and he is delighted to be passing it on and sharing it with his daughter.
Getting to witness sunrise at Newgrange was very special, "it was beautiful. you know, the sun came in, the eyes have to adjust to it first, and then the sliver of sun comes in".
"And it's really something else to think that you're one of a few handful of people throughout history that are standing in there. It's really, it's mind boggling and beautiful and reverent at the same time, very, very interesting," Mr Hennessy said.
Rory McKenna said as he watched the light enter the chamber he thought about the contrast between the technology that is around today and what was available to the builders of Newgrange, 5,000 years ago.
"They were working with the facilities they did have. And what tools did they have? Or how did they go about it? And then at the back of my mind, then, is you have a smart phone now that can tell you where you are to the nearest half metre or something, anywhere on earth," Mr McKenna said.
Solistice celebrated on Slieve Gullion
Meanwhile, In Armagh people walked to an ancient burial cairn on top of the county's highest mountain to celebrate the winter solstice.
The 5,000-year-old burial chamber on top of Slieve Gullion is orientated west so that its inner chamber is illuminated by the setting sun.
At 577 metres it is the highest passage tomb in Ireland and Britain.
Scores of people made a now traditional trek to the top of the mountain to mark the occasion.
They were greeted by a man dressed as a druid who blew an ancient Irish horn to welcome the start of longer days.
The passage tomb has been closed for months pending repairs to the huge cairn of stones.
Locals have called for it to be restored as a matter of urgency.
Additional reporting: Conor Macauley
Read: How Newgrange's spectacular Solstice light show was rediscovered
