I don't think you can get much more rustic than the Trufa holiday home. Built for renowned photographer Roland Halbe's getaway in Spain, the house's construction methods are as interesting, if not more so, than its aesthetic. You wouldn't be able to tell by looking at it, but the house's frame is actually constructed of hay bails.
The construction of the Trufa holiday home started with burying stacked bails inside soil. Concrete was then poured over top and allowed to take shape. Once hardened, the concrete was cut open and hollowed out by--get this--a cow! It ate all of the remaining hay inside so that the workers could get started on the interior. Definitely the most hilarious building story I've ever heard.