On April 1, Apple will unveil an 893,240 square metre advertisement that can be seen from space. According to boakes.org:

The ad, which depicts Apple's flagship iPod product has been constructed on the site of an abandoned mineral mine in remote western Australia. It has been in development for almost two years since Apple's founder Steve Jobs aquired (sic) the location during a game of poker with (the late) Australian publishing and gaming tycoon Kerry Packer.

Check it out in Google Maps (remember, you can zoom in on it).

Appropriately enough, April 1 is the date Apple plans to celebrate its 30th birthday....