Knowth is one of three large passage-graves located at the Boyne valley in eastern Ireland - the others are Newgrange and Dowth. These pictures, taken in September 2010, reveal the astonishing nature of the rock art on the kerbstones at the site. As at Newgrange, it is likely many of these designs have astronomical properties.
The passage-graves on the hill summits at Loughcrew are earlier in date than Newgrange and Knowth. These photos show the presence of the double and tripal spiral motif, and the backstone at carin T may have been carved to represent a ram. Its east-west alignment - the entrance and passage is aligned on the rising sun at equinox - shows that an interest in astronomy - also reflected in the rock art - was well developed several hundred years before the huge Boyne sites were built.