Falak-ol-Aflak Castle is located atop an ancient hill at the heart of Khorramabad and once overlooked the historical Khorramabad Valley in Luristan Province. The benefactor of this castle is unknown but it has been speculated that it dates back to the time of Shapur I the Great (215-270 CE).
At the time, the Sassanids (226-651 CE) had founded a city named Shapur-Khwast near the current city of Khorramabad and used this castle as a military and administrative center. Shapur-Khwast later fell into ruin and the current city of Khorramabad was founded in the 13th century.
Falak-ol-Aflak Castle has an octagonal plan and spans an area of 5,300 square meters and until 100 years ago had 12 towers. Today, the castle has 8 towers, two courtyards, a bathhouse, four large halls and several chambers. Made of stone, adobe and brick with a mortar of lime and stucco, the castle has a 40-meter-deep water well in its first courtyard that once provided drinking water for its inhabitants and is still usable today. The majority of changes and modifications made to the structure of this castle took place from the Safavid (1501–1736) to the Qajar (1785-1925) era.
Throughout history the castle has been known by several names Shapur-Khwast Castle, Sabar-Khwast Castle and Khorramabad Castle. Falak-ol-Aflak is a name that was given to this castle during the Qajar era because at the time it had 12 watchtowers. Others believe that Falak-ol-Aflak denotes the 12 astrological signs or that the castle was virtually impenetrable.
During the Buyid era (934 - 1062) the castle was used as the center of government due to its strategic location. The Badr Vassals ruling under the Buyids used the castle as a treasury and in the Safavid and Qajar eras it was once again used as the center of government. In the Pahlavi era (1925-1979) the castle was turned into a garrison and later a detention center where political prisoners were held.
The castle is currently the location of the Archaeology Museum and Anthropology Museum of Khorramabad. These two museums house earthenware and potshards from prehistory and other historical eras, finds from Kalmakareh Cave, traditional costumes, jewelry, folk instruments, hunting gear, weapons, manuscripts, pencil cases, ink holders, glasses, oil lamps, German silver products, copper vessels, wood products and wax figures showcasing the customs, culture and lifestyle of the people of Luristan Province.
Falak-ol-Aflak Castle has been registered as a National Heritage Site.