That's the Daily Mail's windmill size picture, set beside the Abraj Al-Bait. My hobby is pointing out the existence of this building to people. Please forgive the jpg artifacts and the horrible photoshopping, but the point is, this is to scale. (give or take a few %)
Now, it's not the worlds tallest building per say, but certainly the most collosal thing ever made by mankind. Of course (where else) in Saudi Arabia. As shown schematically in the image, its dimensions are insane x nuts x wtf.
EDIT: fix image link