Qum rugs are woven in workshops of Qum, a city of northwest central Iran. Since rug production did not begin in Qum until about seventy years ago in 1930s, Qum doesn't have any traditional designs of its own. Qum weavers prefer to weave the most favorable designs of other Persian weaving groups and sometimes Caucasian weaving groups and adjusting these designs to their own taste. It is possible for Qum rugs to be mistaken with Kashan or Esfahan rugs. However, they will not be mistaken with Tabriz rugs because Qum, Kashan and Esfahan rugs are woven with the asymmetric (Persian) knot and Tabriz rugs are woven with the symmetric (Turkish) knot. All silk, part silk/part wool, and kork (fine wool taken from the belly of sheep) Qum rugs are very well-known in Iran and abroad. The foundation of Qum rugs could be either cotton or silk.