Cabinets of curiosities (also known in German loanwords as Kunstkabinett, Kunstkammer or Wunderkammer; also Cabinets of Wonder, and wonder-rooms) were encyclopedic collections of objects whose categorical boundaries were, in Renaissance Europe, yet to be defined. Modern terminology would categorize the objects included as belonging to natural history (sometimes faked), geology, ethnography, archaeology, religious or historical relics, works of art (including cabinet paintings), and antiquities. "The Kunstkammer was regarded as a microcosm or theater of the world, and a memory theater. The Kunstkammer conveyed symbolically the patron's control of the world through its indoor, microscopic reproduction." Of Charles I of England's collection, Peter Thomas states succinctly, "The Kunstkabinett itself was a form of propaganda" Besides the most famous, best documented cabinets of rulers and aristocrats, members of the merchant class and early practitioners of science in Europe formed collections that were precursors to museums.
The term cabinet originally described a room rather than a piece of furniture. The classic cabinet of curiosities emerged in the sixteenth century, although more rudimentary collections had existed earlier. The Kunstkammer of Rudolf II, Holy Roman Emperor (ruled 1576–1612), housed in the Hradschin at Prague, was unrivalled north of the Alps; it provided a solace and retreat for contemplation that also served to demonstrate his imperial magnificence and power in symbolic arrangement of their display, ceremoniously presented to visiting diplomats and magnates. Rudolf's uncle, Ferdinand II, Archduke of Austria, also had a collection, with a special emphasis on paintings of people with interesting deformities, which remains largely intact as the Chamber of Art and Curiosities at Ambras Castle in Austria.