Abstract
The tombs or funerary monuments are one of the most important elements of Iranian-Islamic architecture that in different fields require careful investigation. This group of buildings is important among Iranians; for this reason, in each period of the Islamic era of Iran the most important and most used arts related to that period have been used in their construction. Generally, the decoration in buildings has a more effective role, because, if it is understandable in terms of form and structure for archaeologists and designers, it’s possible this isn’t understandable for the general public. So, decorations in the buildings at first sight are attracts the viewer. In this article epigraphy art as one of the most important decorative elements of Islamic buildings have been reviewed in the four Seljuk tombs of Northwest of Iran: Gonbad Sorkh, Borj Modavar in Maragheh, Seh Gonbad, and Gonbad Kabood. The research method in this study is interpretive – historical. In this study with analytical method have been studied decorations of these four tombs (especially in terms of architecture, motifs, inscriptions and their position on the buildings). Also, in addition to reviewing the articles, books, and evidences, with field survey from these tombs, plan and decorations, and then a comparison table of inscriptions has been provided. In this regard, the following questions are raised:
- How is architecture, motifs and decorations of the Seljuk tombs in northwest Iran? And, their inscriptions are divided into several categories in terms of content?
- What are the effects of concepts of the inscriptions on position them on the buildings?
Reviews show that inscriptions of Seljuk tombs in the Northwest are divided into four groups: The Quranic verses, inscription with the theme of the date of construction, inscription with the topic of prayer, and inscription with the theme of the architect and the builder. On the other hand, position these inscriptions in the buildings have been differed proportional in their content. Inscriptions of the Quranic verses in the highest section of building, inscription with topic of prayer in the lower, inscription with the theme of date of construction and architect and builder are placed on the lower levels and on the body of building.
Keywords: Islamic architecture, Seljuk tombs, Northwest of Iran, decorations, inscription.

Introduction
Generally, one way of cognition more about periods of Islamic architecture besides of decorative elements and motifs, is study of inscriptions and their texts. In the Seljuk period, one of their architectural features, are create inscriptions and decorative lines from shaved bricks, that in most of buildings this period (especially tombs) is seen. Furthermore, due to the difficulty of shaving the bricks and the formation of letters and words with it, during this period, the Naskh script was replaced by the Kofi script and inscription with style of stucco was used (Hatam, 1999: 162).
In this article, in addition to reviewing the historical background and the process of build tombs in the Seljuk period to study and compare four tombs in the Seljuk period in Northwest of Iran, first have been introduce architectural features and decorative motifs them. Then, in comparative tables have been specified types of inscriptions and their position on the tombs. In this regard, following questions are raised: How are architecture, motifs and decorations of the Seljuk tombs in northwest Iran? And, their inscriptions are divided into several categories in terms of content? And, what are the effects of concepts of the inscriptions on position them on the buildings?
This study shows, inscriptions of Seljuk tombs in the Northwest are divided into four groups: The Quranic verses, inscription with the theme of the date of construction, inscription with the topic of prayer, and inscription with the theme of the architect and the builder. On the other hand, position these inscriptions in the buildings have been differed proportional in their content. Inscriptions of the Quranic verses in the highest section of building, inscription with topic of prayer in the lower, inscription with the theme of date of construction and architect and builder are placed on the lower levels and on the body of building.

Buildings under study
Gonbad Sorkh: The Gonbad Sorkh is oldest tomb in the Maragheh that is located in the southern part of the city and west side of Hashtrod road. Generally, in the Gonbad Sorkhon and in different parts and also on all sides this tomb is inscription.
Borj Modavar: The Borj Modavar is second tomb built after the Gonbad Sorkh and inside the city of Maragheh. This tomb now is located in Khaje Nasir Street and behind the building of Bank Melli. The Borj Modavar has two inscriptions that both of them are located in the main direction of the building and facing the North. 
Seh Gonbad: The Seh Gonbad is third tomb that was built in the Seljuk period in Azerbaijan. This tomb is located in the southeastern of Urmia city. The three inscriptions with Kofi script and geometric motifs at the facades of this tomb have created beautiful view.
Gonbad Kabood: The Gonbad Kabood after the Gonbad Sorkh and the Borj Modavar is third of building that has been made in the Maragheh city. In this building 5 inscriptions are visible.

Conclusion
It’s certain, in Seljuk period and in the method architects and artists of this period, concepts of inscriptions have played an important role in location of inscriptions. According to this, inscriptions of Quranic verses and inscriptions of mystical concepts and prayers have usually been located at higher levels. Other inscriptions (such as inscriptions with historical or political themes) have usually been located in lower levels. The location of inscriptions in buildings from the down to up in four sections 1, 2, 3, and 4 in the table below is shown.