On 21 December - the shortest day of the year - the sun shines deep into the tomb in County Meath, flooding the neolithic chamber with light.
But poor weather dampened celebrations this year. The sun's rays should have entered the chamber at 0858 GMT on Sunday. But cloudy skies meant this failed to happen.
Usually, at the solstice, as the sun's rays clear the horizon, they illuminate, in perfect alignment, a 19-metre passage and chamber.
In the days before Christianity, festivals were held around the winter solstice to welcome back the longer, lighter days and pay tribute to the Sun.
-Article continues off site, courtesy BBC News.
