The Kaiserliche Schatzkammer Wien (Treasury) offers a unique panorama covering over a millennium of European history. This is the home of the most important collection of medieval royal objects: the insignia and jewels of the Holy Roman Empire, including the Imperial Crown and the Holy Lance. Further highlights include the Crown of Emperor Rudolf II. (which later on became Crown of the Austrian Empire), as well as the vestments and other precious items of the Order of the Golden Fleece. Exceedingly valuable gems, including one of the world's largest emeralds, bear witness to the Habsburgs’ former degree of power. In earlier centuries, two items were considered to be so unique that they were declared “inalienable heirlooms of the House of Austria”: a giant narwhal tooth which was thought to be the horn of a unicorn and an agate bowl from Late Antiquity which was thought to be the legendary Holy Grail.