Artist duo Skrekkøgle (Theo Tveterås and Lars Marcus Vedeler) created a 20:1 replica of the 50-cent Euro coin to make other thinks look small when photographed next to it. The coin was actually milled, sanded, lacquered and smudged to maintain authenticity.

Then they went out finding various objects around the city to miniaturize. To help achieve the effect the duo tries to find elevated vantage points and also employ the tilt-shift photography effect by using special lenses or blurring the top and bottom third of the image in post. You can see the results of this great exploration below.
 
For a tutorial on creating your own giant coin, visit: http://www.skrekkogle.com/coinhowto.html
 
To see more projects by Skrekkøgle, be sure to check out: http://www.skrekkogle.com