Knowth is a passage tomb within the Brú na Bóinne World Heritage site. It has more than 200 decorated kerbstones with the “Sundial” Kerbstone being the inspiration for this design. It has very distinctive engraving of lines, radiating outwards in a semi circle “starshape” with a dot in the centre, prompting many to suggest it may have been a form of sundial. One astronomical theory suggests that the art represents solar, lunar and stellar images and cycles. The stone age people who constructed the monument, unhindered by artificial light, would have observed nightly changes in the moon and constellations of starsbmapped out in animal shapes, changing their position. Much of the artwork at Knowth could represent celestial worship.