One of the best known aspects of the passage cairns are their art, an uninterperetated symbolic language that ornamentats many of the stones, especially in County Meath. These engravings are the earliest writings in Ireland and among the oldest in Europe. They are documents in stone written in a symbolic language which seems to incorporate the light and motion of the heavens.
That these engravings deal with astronomical themes is demonstrated in several sites, where the artwork is illuminated by the light of the sun or moon at a chosen time in the cycle of the body in question. This is demonstrated at Cairn G , Carrowkeel (no artwork), Cairns L and T, Loughcrew and Boyne Valley sites in these pages.
Knowth alone has 50% of the engraved stones in Ireland. Early engravings have been discovered in recent years on the chamber of Listohil monument at Carrowmore in Co Sligo. Heapstown Cairn, also in Sligo is known to have had several engraved stones, with perhaps an ogham stone standing at the top of the mound. Only one stone remains visible today, as many were robbed from the site in the last century.
Neolithic art on a passage stone within Cairn F on Carnbane west. Zig-zags, undulating waves and diamond shapes, the latter thought to be ancient units of land measurement by researchers Martin Brennan and Michael Poynder.
The so called Guardian stone or Owl man at the bend in the passage of Knowth west. The neolithic art is deeply scratched, probably by the later medieval graffiti artists who left at least 20 ogham names on the stones of Knowth.
Large and beautiful panel from a roofstone in the passage of Knowth east.
This stone was found lying in the medieval ditch that encircles the mound of Knowth, and was restored as a passage stone during the 'restoration'.