A carpet is a textile floor covering consisting of an upper layer of “pile” attached to a backing. The pile is generally either made from wool or a manmade fibre such as polypropylene, and usually consists of twisted tufts which are often heat-treated to maintain their structure. The term “carpet” is used interchangeably with the term “rug”. The hand-knotted pile carpet probably originated in the Caucasus between the 3rd and 2nd millennium BC. Cilician Armenia which had intensive trade relations with Venice, brought carpets to all of Europe, where they were primarily hung on walls or used on tables. Only with the opening of trade routes in the 17th century were significant numbers of Persian rugs introduced to Western Europe.