On the southern hillside of the Central Alborz Mountains, in the province of Tehran, there are many castles, forts, and defense facilities from different historical periods that have not been studied much before this research, and little information is available about them. This research was done analytically to answer questions: What is the number and background of the construction of castles in Tehran? How many categories are they divided into according to Typology (archaeology)? What is the pattern of the spatial organization? It was assumed that in Tehran province, due to climatic conditions, geographical location, and political and social conditions, castles from pre-Islamic and Islamic eras were erected and divided into two main types, mountainous and pasture. Castles have particular spatial organization according to the place of construction and the builders' goals. In terms of form, they include two categories of regular and irregular geometry, and in terms of function, they are divided into residential and military types. The information needed for this research was collected using library and field studies. The field study was performed by surface surveying, remote evaluation, and the cultural data necessary were documented and recorded. In the present study, which led to the identification and documentation of 159 defensive constructions and buildings in Tehran province, it was found that castle construction in Tehran province began in the Median period and developed in the Parthian and Sasanian eras and bloomed in the Islamic period, especially the middle ages.