Contemporary rooftop gardens are meager attempts of a very old practice. Ask any Icelander for verification. Green roofs, like those found in Iceland, have been around for centuries. Yes, settlers of the U.S. Midwest had their sod houses, but these Icelandic creations make them look like child's play.
For more information on the history of Icelandic turf houses, and to see more gorgeous pictures, follow this jump to Greenfab.