The stone may have been used for making lunar calculations, and features a number of large conspicuous crescent shapes which may represent early and late phases of the moon. The photo below shows the concrete wall which was being built right in front of the stone - the picture may be deceiving because it was taken with a wide angle lens, but the wall is about 2-3 feet from the face of the stone. On a later visit to Knowth, after completion of the wall, I found it difficult to find a position where I could see any detail on the face of the stone.

Archaeological work has been ongoing at Knowth for nearly 40 years. This was the very last stone to be uncovered during excavations, and was the very first to be blocked up again. The wall was being built to support a ramp to facilitate the movement of tourists up to the top of Knowth via a Norman 'trench' which was dug into the mound on this side some centuries ago.

Other stones at Knowth and the ancient Boyne sites show that the Stone Age people had a huge knowledge of the workings of the heavens. There is some evidence that they understood the lunar cycle, known as the Metonic Cycle, and were able to predict lunar eclipses. Above is a selection of images showing some of the conspicuous crescent, or lunar, symbols at Knowth.