The Bird's Nest by Inrednin Gsgruppen

This huge nest with a retractable staircase by Swedish designers Inrednin Gsgruppen forms part of a hotel in the trees in northern Sweden. Part of the Tree Hotel, The Nest is supported by existing trees and the exterior is covered in twigs.

http://www.dezeen.com/2011/05/27/the-birds-nest-by-inrednin-gsgruppen/