The first prayer rugs were made in Ushak during the 16th century. Also called Bellini rugs, after the Venetian painter Giovanni Bellini (ca. 1432-1516), there are decorated by a mihrab, usually red, within which is a medallion, and can be recognized by the form of the niche, the lower part of which resembles a keyhole and bears in turn a small medallion.
The layout of the prayer rug also appears in the so-called Tintoretto rugs, named after another celebrated Venetian artist (1518-1894), which are more properly known as double-niche Ushaks because of the hexagonal shape of the medallion, a result of joining two specular niches. The use of a central rosette and four side ones creates the same type of nondirectional structure found in medallion carpets, but the mosque lamp hanging from the end of the rosette often gives these rugs the directional sense typical of prayer rugs. Usually small cloud band borders, this 16th layout became widespread beginning in the 17th century.
(The bulfinch guide to carpets /Enza Milanesi)