My mate told my about this yesterday. Its basically like a huge urban treasure hunt that you do with your smartphone. All over the world there are these hidden ‘caches’, and they are literally everywhere – I found 4 within 500m of my house today. People hide something, then post rough GPS co-ordinates online and a clue to the exact location of it. E.g. today my phone took me to a busy train station and there was a film canister with tiny magnets in it clipped to the underside of a pedestrian bridge over the tracks. It’s been there for years too without anyone nicking it – you just had to know where to look. Usually there’s not much in them other than a little book to write your name in and maybe some random toys and stuff, but its pretty satisfying to do.
Geocaching – The Official Global GPS Cache Hunt Site
You can do a postcode search on here and it will come up with a map showing all the nearest ones to you.
