Three German architects created this bird-watching station in Bavaria using fast-growing willow trees as the sole supports. They call the technique "arbo architecture."
Ferdinand Ludwig, Oliver Storz, and Hannes Schwertfeger begin with a metal scaffolding onto which they bind the young trees. As time passes, they slowly remove the support structure and allow the trees to bear the load. After a few years, the structure is ready for a "botanical certificate of fitness" in which a structural engineer inspects their handiwork for safety. The trio is now at work on a larger arbo architecture building in Stuttgart.