Espahbad Khorshid cave is one of the giant natural arches in the world, which has a fantastic architecture of the late Sassanid Age. Inside this arch, we encounter architectural works of the Sassanid Age, built of stone rubble and Saroj mortar. The purpose of this research is to study the architectural works of this site and compare them with other architectural works of the Sassanid Age in other parts of Iran. The question of this research is, what are the similarities between architectural works discovered in Espahbad Khorshid cave and other architectural works from the Sassanid Age? The research hypothesis in answering this question is the use of stone rubble, Saroj mortar, rocking arches, and crescent arches in Espahbad Khorshid cave shows the significant similarity of this architecture with Sassanid Age architecture. This research uses fieldwork and documentation of architectural works discovered in Espahbad Khorshid cave. The results show that the architecture in this cave is significantly similar to the architectural works of the Sassanid Age in other parts of Iran. One of them is Dokhtar castle in Firuzabad, Fars province. Therefore, we can say the architectural works discovered from the Espahbad Khorshid cave are one of the unique architectures of the late Sassanid Age found in the Mazandaran region, and in terms of architecture, historical Age, and height of the castle has significant importance.