Loughcrew

The Cairns are megalithic structures originally built about 4000 bc as burial chambers. 

The Megalithic Cairns are dotted around the Slieve na Caillaigh hills at Loughcrew, the main concentrations are on Carnbane East where Cairn T is the centrepiece and Carnbane West where Cairn L is located. The illumination of the passage and chamber at the Winter solstice sunrise in Newgrange is world famous. Less well known is the Equinox illumination at sunrise in Cairn T at Loughcrew. The backstone of the chamber is illuminated by a beam of light at sunrise on the Spring and Autumnal Equinoxes.

The sun light is shaped by the stones of the entrance and passage and descends the backstone while moving from left to the right illuminating the solar symbols. 
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Sources:
The Knowth
Loughcrew Gardens 
Meath.ie
Mega Lithic Ireland
Mythical Ireland
Carrowkeel
Voices from the Dawn