Iraj Castle

Iraj Castle ( Qal'eh Iraj) is a fortification built in 4th or 5th century AD in the central region of Ray, Sasanian Empire, near modern-day Asgarabad-e Abbasi, Iran. The monument is known for its peculiar design: large defensive walls with embedded rooms and arches, with towers at regular intervals, enclosing a vast empty interior of 190 hectares (470 acres).

The design is similar to several other Sasanian campaign bases. The permanent service members supposedly occupied the walls and the rooms inside it, while the empty interior would be occupied by tents or used for training or military assemblies. It probably served as a central military base for operations elsewhere, especially against the incursions of nomadic nations in the north.

Description and purpose
The structure consists of an empty area approximately 175 ha, surrounded by a wall 15–22 m in width and up to 25 m in height. It featured 148 densely spaced towers and four monumental gates. The massive walls contained a wealth of embedded structures: a row of around 828 rooms (circa 12 m2 in size) and hundreds of monumental arches, evoking royal Sasanian architecture. The structure was further protected by a ditch around the wall. A population of 2,000-6,000 could have been accommodated in the walls. Despite this strong architectural focus on the walls, there were no permanent buildings in the interior space.

A total of about 50,000 warriors could have comfortably occupied the structure. The rooms may have housed the permanent garrison, while the open interior space was occupied temporarily.

Qaleh Iraj was probably built in response to northern nomadic invaders which, on some occasions, penetrated deep into the Sasanian territory. It probably functioned mainly as a central base for military operations elsewhere, especially at the northern frontiers. It may have been used for military training and/or military assemblies as well. The 36 ha campaign base at Gabri Qaleh near Gonbad-e Kavus was built in the same period. Both thus predate the Great Wall of Gorgan. These Sasanian campaign bases may have been built before the northern frontiers were protected by the linear Sasanian defence lines.

The region Ray was suitable as a central base from several aspects. Sitting at the center of Greater Iran and on a central communication hub, it was always a militarily significant region. Plus, it was also the base of the powerful House of Mihran during the Sasanian period.

Current status
Parts of the walls have been eroded, and out of the four gates, only the main, southern gate remains today. Iraj Castle is considered as the world's largest mud-brick fort with a height of 50 feet and an area of 200 hectares.

There have been attempts by the Cultural Heritage, Handicrafts and Tourism Organization of Iran in 2008 to designate it as a UNESCO World Heritage Site, but the efforts were abandoned due to "serious shortcomings" and the situation of the area, including the agricultural activities of local farmers in the interior of the structure.

Illegal excavation have damaged parts of the walls. On 26 May 2018, an illegal excavation was reported in the Northern Gate. Majid Zhaleh, the head of the Cultural Heritage, Handicrafts and Tourism Organization of Pishva County, stated that his organization lacks enough manpower.