Sassanid art and especially its architecture which was influenced by the art of other ethnic groups and civilizations of its time showed many innovations in various fields, including the proper use of gypsum in the decoration of buildings. The Sassanid style of architecture provided a suitable platform for the expansion of arrays. The decorative motifs used in various buildings of the Sassanid period include plant, geometric, animal-human, and script motifs that were influenced and expanded during the Islamic period and influenced many other arts as well. The Jameh Mosque of Urmia, known as the jumʿah Mosque, was formed in different periods so that each part of it belongs to a specific period. The altar of the mosque is located in the dome chamber and has many decorative designs of various geometric and arabesque types; In addition to showing the characteristics of the stucco art of the Ilkhanate era, influences of its antecedent period, that is, Seljuk and the pre-Islamic period, especially the Sassanid period are observable. In addition to multiple decorative motifs and elegance used in this altar, the use of various scripts such as Kufic, Thuluth, and Reqa is also very important in influencing the audience. The purpose of this study is to identify the decorative arrays influenced by the decorative motifs related to Sassanid architecture in the altar of the Jameh Mosque of Urmia. Based on this, the following two questions have been raised: A- Are the motifs and arrays used in the decoration of the altar of the Jameh Mosque of Urmia are affected by the motifs of the Sassanid period? B- Which elements from the Sassanid period are included in the motifs adapted in the altar of the Jameh Mosque of Urmia? This research uses a descriptive-comparative method. A combined method (library and field) has been used to collect data. Data collection tools also include identity graph (ID Graph), photography and observation. To provide the possibility of comparison and matching, first, the information related to each of the decorative motifs of the altar of Jameh Mosque of Urmia and the motifs related to Sassanid architecture were classified separately, and then to analyze the existing motifs, tables were designed and the mentioned motifs were comparatively examined. The results of this study indicate that in the Islamic era, decorative motifs using the pre-Islamic heritage of Iranian art have been used. The results of this study indicate that the arrays used are influenced by the Sassanid period and the plant motifs in the stucco of the Sassanid period such as dragon's mouth-like and elephant's trunk-like in altar are in arabesque and khitan form and in the form of various arabesques such as dragon's mouth and elephant's trunk have evolved with many details. Similarly, Kufic and Thuluth scripts have also been used in the context of these motifs. Geometric motifs also show a more complex shape of geometric motifs of the Sassanid era. Circles and triangles have been frequently used. There are also motifs such as multi-petal flowers or florets with varying number of petal, hexagonal, octagonal and sixteen-petal that have been used in the decorative arrays of Ctesiphon Palace and Chal Tarkhan Rey stucco and kish's Elit Palace stucco belonging to the Sassanid period; In many cases, with modifications, they have been used in a way similar to the previous shapes and forms. In addition, the use of palm leaf motifs, spoon-like motifs, multi-petal flowers, and some motifs such as pomegranate flower motifs that have existed for a long time in Sassanid palaces, have been executed very easily in the columns of the altar. In addition, many plant motifs of the Sassanid period, such as grapevines, pomegranates, palms and acanthus leaves can be seen in combination with arabesque motifs in the altar of the mosque. Also, the leaves of multi-leafed palms, which cover the cornices in various shapes in the form of three, five or seven leaves in the Sassanid period, are used in the decoration of the altar inscriptions, in combination with the script, so that in some parts the three-leafed palm leaves appear in full shape. Elsewhere, a three-leafed palm leaf is halved and used as a two-leaf. Palm leaves, which are sometimes implemented in some cases as singular with smaller palm leaves; in the embossed stucco of kish's Elit Palace, it is shown that various decorations have been done on the leaves. This use of singular palm leaves can be seen in the altar stucco of the Jameh Mosque of Urmia on which geometric decorations have also been worked on them. Another point is that among the decorative motifs of the altar, the basic and the simple motif of Shah Abbasi flowers can be seen in the rib half-vault of the altar of the Jameh Mosque of Urmia, which is interesting in its kind.
