During different human periods, many factors have influenced the formation of cities. Sometimes one or more factors constitute city including mountains, rivers, building, roads, religion, and customs. Religion as a cultural element is the source of change and difference in various countries. The orders of Islam religion is such that they can be achieved easily in urban environment. Then Islamic governments were established, and city development was their goal to show their strength and achieve idealistic, social and political purposes. Ideals and duties of Islamic government embody in the city. In Islamic period, the first example of impact of on building as a religious factors in city development can be identified as prophet’s mosque in Madineh city. Religious buildings have a great influence in formation and development of many cities in Iran and in Islamic realm. Considering their abundant historic, artistic, religious and social impacts on architecture, focusing on these buildings can lead to creation or development of cities in this territory to be introduced as a tourist destination and exhibit the architecture of Islamic city. Ilam province, located on common borders of Iran and Iraq on the direction of migration and exile of Alevis, is home to many Imamzadeh and their companions Shrines in its cities and villages due to the impassable mountainous. This study aims to investigate the effect of Ali-alsaleh Shrine (pbuh) as a cultural and religious element in the formation of Saleh Abad city located in Ilam province. According to library and field studies and based on history of the shrine existence in Hegdandasht region and the prepared development map of city, it can be conclude that this shrine as a religious tomb building in Islamic period is the only factor of city formation and growth in a hot and arid climate. Noted city has taken its name from this shrine, and has been known as Saleh Abad.