Over the years it has been proposed that the carvings on the orthostat within The Mound of the Hostages are art work, celestial representations or even a calendar. However, a regular visitor to this site has theorized that they actually correspond to the monuments on the Hill of Tara.
While this theory has yet to be confirmed, it offers a rather interesting view of how Tara may have really evolved and suggests that it played a far more important role than previously thought. If correct, it would further support the argument that Tara, like Newgrange and Knowth, should be named a World Heritage Site.
Read the full article at http://www.knowth.com/tara-orthostat.htm