Archaeological studies on the margins of the Central Desert and Lut Desert of Iran indicate important roads which have been created to connect cities and populated centers, and the presence of architectural remains, especially the caravanserai on the side of these roads, shows their importance. These roads have been built for various economic, military, social, cultural and other purposes. Crossing desert roads, in addition to harsh environmental conditions and the distance of villages and cities from each other, posed a risk of bandits attacking caravans and passers-by. Therefore, in addition to building resorts which sometimes had defensive structures, the governments of that time construacted other structures such as castles and military towers on the important roads to supply security. In terms of architectural use of castles, there is a lot of diversity, and according to its use and location, it is different in size and architectural spaces. However, most of these structures are important from a defensive point of view and are examples of military architecture. Moshkour Castle located in the Nayband, a protected Area of South Khorasan, is one of the most important defense structures on the Khorasan-Kerman road. This castle was probably built in the Safavid to Qajar period to protect the caravans crossing this important route which connected the cities of central and southern Iran to northern Khorasan. The research method is descriptive-analytical and data was collected in a field and library method, then data was analyzed using historical documents such as geographical books and travelogues. The main question of this research is that what is the role of Moshkour Castle in providing security in the region and the margin of Lut desert? And are other structures designed around it? The results show that to provide the security of important roads passing through the central cities of Iran, especially the deserts, the defense and military structures have been constructed to secure the lives and property of the caravans, adjacent to this castle and storage basin to settle passengers and caravans along the Khorasan and Kerman roads. In fact, the architectural spaces of the stuied area have been constructed between the two houses of Cheshmeh Abgarm and Nayband caravanserai.