One of the mos t important principles in the formation of Iranian-Islamic cities is the principle of unity. Observing the principle of unity in the physical-social space of his torical neighborhoods has led to the organization and integration of them. A review of s tudies on this issue indicates that the principle of unity in the scale of urban neighborhoods has been less considered. The main ques tion of the s tudy is how and with what factors and criteria was the principle of unity formed in the physical space of Sarshoor neighborhood, Mashhad city? This s tudy is his torical and analytical research. The research process is divided into two main s tages. In the firs t s tage, it is attempted to determine how the spatial s tructure of the Sarshoor neighborhood was before the extensive physical-spatial interventions taken in the contemporary era. In the second s tage, the factors and criteria related to the principle of unity are determined on the maps and photos of the neighborhood in an exploratory way and using the relevant graphical analysis. The results show that in the his torical neighborhood of Sarshoor, a set of factors in a complex and close relationship with each other, have been effective in unifying the physical space of the neighborhood. Factors including "connectivity and continuity", "centrality", "hierarchy", "coordination", "interconnectedness" and "semantic unity" have been effective in realizing the principle of unity in the neighborhood by creating various qualities in different dimensions of physical space of the neighborhood.
