Sunlight enters the main entrance of New Grange once per year on the Winter Solstice (Cyril Byrnes, via The Irish Times)

Happy St. Patrick’s Day! As people all over celebrate all things Irish today, let’s take a look at a place as old as Ireland itself. New Grange is a huge passage mound in County Meath that dates to 3100 – 2900 BCE, during the Neolithic Period (the New Stone Age). It is part of the Brú na Bóinne archaeological complex, an expansive site that predates the Pyramids at Giza. Roughly 150 passage graves survive today in Ireland and 40 of them are locate at Brú na Bóinne.

The site is huge. Some 550 giant slabs, weighing a total of 200,000 tonnes were quarried from the riverside nearby in order to construct it and transported to the site, all under the power of humans and animals. Its use is uncertain, though most people believe it was a tomb. It does have some astronomical significance as well: Each winter solstice, the sun shines directly into the main passage of the monument, illuminating the far wall.

Wikipedia: New Grange