It turned out that Mr Monkey had found the Angel of the North. This is a 20 metre high statue on a hill outside Gateshead, and is apparently not only the largest sculpture in Britain, but also the most frequently seen (sticking it on a hill near a major road junction might have something to do with this, of course). On closer investigation, Mr Monkey found that the Angel's feet make a good slide.
There's all sorts of information about the Angel at the Gateshead Council Angel website.
Copyright Rik Shepherd and Mr Monkey. This page last modified 29 October 2003