21 December 1967: The rediscovery of the sunlight in the passage tomb at Newgrange Co Meath on this day. On this morning in the midst of Winter Professor Michael J. O'Kelly stood alone in the passageway and watched as the first rays of sunshine struck the inside of the walls of the chamber at the time of the winter solstice. Also known as midwinter, it is an astronomical phenomenon marking the days with the shortest periods of daylight and the longest nights of the year. The structure was built by ancient Neolithic [New Stone Age] people some 5,200 years ago (3,200 B.C.) which makes it older than Stonehenge and the Great Pyramids of Giza. 

While a dominant feature on the landscape today it was buried for centuries and only identified as an ancient site at the end of the 17th century. However a modern scientific excavation just began in the early 1960s led by a team of archaeologists under Professor O’Kelly. He was easily the best qualified man in Ireland to undertake the task having decades of practical experience and a formidable academic record behind him in surveying, architecture and archaeology. Talking to locals he discovered that there was a persistent tradition that at the time of the Winter Solstice that as dawn broke on that day the light of Sun entered the chamber and struck the back of it onto the three spirals carved into the rock face. 

The Professor was intrigued by this and by December 1967 he could stand it no longer. He set out from his home in Co Cork and made the long journey up to County Meath to check it out for himself. 

Some minutes before sunrise on the 21st of December 1967, Professor O'Kelly stood alone in the darkness of the chamber at Newgrange, wondering what, if anything, would happen. To his amazement, minute by minute, the chamber grew steadily lighter and a beam of sunlight began to enter the passage and to travel inwards, "lighting up everything as it came until the whole chamber – side recesses, floor and roof six metres above the floor – were all clearly illuminated". O'Kelly stood rigid for a while, transfixed by the phenomenon and convinced and fearful in his own imagination that the Dagda, the sun god, who according to the ancient tradition had built the tomb, was about to hurl the roof upon him.
Fortunately the roof remained in place, the sun retreated and he walked from the tomb, the first person to have witnessed the light of the sun penetrate the darkness of the chamber at Newgrange since ancient times.
http://www.newgrange.com/michael-j-okelly.htm

This re-discovery and the development of the site into a recognisable structure once again brought the magnificence  of the place and that of the other passage tombs Knowth and Dowth at Brú na Bóinne  [Palace or Mansion of the (river) Boyne] to the attention of the World of Archaeology. 

Today Newgrange is one of Ireland’s top tourist attractions with some 150,000 visitors  per annum. This time of year draws people from around the World who come to take inspiration from the site. Even if they have little chance of entering the chamber at the golden moment or even of seeing anything at all on a dull morning can still be moved by the majesty of the place - and feel a link to our stone age ancestors and the great skills in engineering and astronomy that they surely possessed.