in the space between the inner and outer dome of St Paul's there are things carved no one ever sees and there is a cup mark on top of the a stone at stonehenge no? there was that amazing scene in C S lewis's 'The Silver Chair' where various trenches the kids were stumbling about in turned out to spell 'UNDER ME'.

I love the fact you might never have erally realised it was a horse but it was still important to the people who made it that it was....or perhaps with hallucongenics they could get high enough to see it properly.....