Falak-ol-Aflak is one of the most impressive castles in Iran. It is situated on the top of a large hill with the same name within the city of Khorramabad, the regional capital of Lorestan province. This gigantic structure was built during the Sassanid era (226–651).Falak ol-Aflak castle is amongst the most important structures built during the Sassanid era. It has been known by a number of names since it was built over 1800 years ago. Recorded names have referred to it as Shapur-Khast or Sabr-Khast fortress, Dezbaz, Khorramabad castle, and ultimately the Falak ol-Aflak Castle.