I was in Poundland on Saturday and grabbed up one of these. It's a stepping stone for your garden, and they come in a variety of different designs -- a compass rose, this sun thing and a more moon-looking symbol were the ones I saw, but there could be more. I think it will make a rather nifty feature for dungeons or Frostgrave or wherever.
Here it is in use as a summoning circle for a wizard to bring forth a djinn.
Pretty substantial; not bad for a quid. And a useful reminder that good gaming stuff can turn up more or less anywhere; just keep your eyes open wherever you go.