In the history of Iranian territory, attention towards defensive fortifications has always ambitiously been concerned as an important factor for survival of the residential and governmental centers. Detailed and precise focusing on each of these defensive structures will provide useful information on the characteristics of this type of military architecture. An MW 6. 5 earthquake devastated the town of BAM in southeast Iran on 26 December 2003. After the BAM earthquake, attentions have been attracted towards Arg-e-BAM complex which had been extensively damaged, and methodical studies were initiated in various parts of this world heritage site. The citadel is located on the northeast of BAM, a dependency of Kerman province located 193 kilometers southeast of Kerman (the province center) and 1257 kilometers southeast of Tehran. The citadel consists of two main areas, the ruler’ s seat and the commoners’ area, which are separated by walls and watchtowers. Another wall, lined by a moat, runs approximately 2, 000 meters around this ensemble, separating it from the surrounding fields. Hence, the present study was being carried out from 2005 to 2008, and aimed at introducing and recognizing the main structure of Arg-e-BAM defense system. In this research which has based on a scientific viewpoint and a logical analysis focusing on findings, elements observations and architectural bodies obtained from a part of the fence between towers (8) and (9) on the southern (main) front up to reaching the ditch and also from new-found parts of the fence body, it has been shown that the image formed in pictures, reports and public opinion about the nature of BAM citadel defensive structure was actually a part of it, as a volume of accumulated historical debris caused by demolitions and reconstructions during the past centuries, which can be seen as a ramp adjacent to the fence up to reaching the ditch and around all sides of the citadel. Understanding the physical situation and constituting layers of this massive defensive structure at the corner of Lut Desert will be useful for researchers not only to know about the architectural aspects, but also to better understand the socio-political conditions of governmental structures during different historical periods in this area. According to the revision of Arg-e-BAM defensive fortifications based on the field studies and explorations, new-found parts include an extensive wall located between the ditch and the fence wall with a height of 2. 7 m, which is larger than the human size, and the ramp which is elevated from the top of this wall to fence base, expressing its defensive role as an obstacle preventing the invaders from easy access to the fence side, and stressing on its role as an strengthening element for retrofitting the citadel defensive wall structure from the structural engineering viewpoint. Evaluating the natural ground bed of the area and the artificial effects created by human activities on the area, detailed studying and scientific perceptions about the manner of positioning and distribution of various defensive elements relative to each other, and detecting the level differences between Sharestan (public stand) bed, fence and fortifications, ditch and the natural ground bed around the complex indicate that there have been extensive changes in the complex area in order to construct the spaces and architectural body of Arg-e-BAM complex as a world heritage site. Findings have suggested the use of ground bed soil as brick and clay materials for the construction of BAM structures and its architectural components. This study has been accompanied with field exploration, mapping and analysis of findings, along with a reviewing of the books and documents available on BAM and defensive fortifications and structures, and with the guidance given by experts.