This is the front entrance of New Grange in Ireland which was built over 5,000 years ago. It predates the Pyramids and Stone Henge in the British Isles. It is in line with the Winter Solstice where the light from the rising sun will shine through the port hole above the entrance all the way to the back of the chamber on the Solstice. This marked the shortest day of the year and gave comfort to the people knowing that the days would become longer from this point on and into the Spring.
Happy Solstice!