The western entrance of Knowth Passage Tomb Cemetery. At sunset on the equinoxes, the sun casts a shadow from the orthostat on the kerbstone in the centre of the image. There is a corresponding orthostat on the other (eastern) entrance of the mound, which carries out a similar function at sunrise. The quartz stones on the ground in fromt of the entrance come from Wicklow in the south; the round granite rocks scattered amongst them come from the Mourne mountains to the north.