Falak - ol - Aflak Castle Falak - ol - Aflak Castle ( in " Dež - e Shāpūr - Khwāst " , in ancient times known as Dežbār as well as Shāpūr - Khwāst ) is a castle situated on the top of a large hill with the same name within the city of Khorramabad , the regional capital of Lorestan province , Iran . This gigantic structure was built during the Sassanid era ( 226 – 651 ) . The Khoramabad River runs past the eastern and south - western side of the Falak - ol - Aflak hill providing the fortress with an element of natural protection . Today , the western and northern sides of the hill are bordered by the residential districts of Khorramabad . History . 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 , Khoramabad castle , and ultimately the Falak - ol - Aflak Castle . During the Pahlavi dynasty it was used as a prison . Architectural layout . The foundations of the actual castle measure approximately . The height of the entire structure , including the hill , reaches to 40 meters above the surrounding area . The castle itself covers an area of . The perimeter extends for in perimeter and its tallest wall is 22 . 5 metres high . This space is divided into four large halls , and their associated rooms and corridors . The rooms all surround two courtyards with the following measurements : the first courtyard measures and the second . When originally built the castle used to have 12 towers , but only eight remain standing today . The building ' s entrance is situated towards the north , within the body of the northwestern tower . The water well of the fortress lies in the area behind the first courtyard . Reaching a depth of 40 meters , the majority of the well ' s shaft is carved into the rock in order to reach the source of the Golestan spring . The well remains usable to this day . The materials used in the construction of the fortress are mud - bricks , mud - fired bricks , stone , wood , and mortar . Surrounding structures . Archeological studies have identified the existence of a two layered rampart with twelve towers around the present day construction . This surrounding rampart mainly stretched westward . From the twelve original towers , only two remain and these are situated northwest and southwest of the existing fortress . Dehumidifier . Falak ol - Aflak Castle appears to have been built with a dehumidifier system . Previously , the experts believed these dehumidifier canals with a height of more than 1 meter covering all the area beneath the castle were hide - outs for the residents . But in reality , due to being aware of the changing climate in the region and the underground waters , the Sassanid engineers have equipped the castle with a dehumidifier . Falak ol - Aflak castle is made with different materials like stone and wood that are vulnerable to humidity . That is why the castle was built on the highest point of the city of Khoram - abad , so that the wind could penetrate the building and dry its foundations . Current status . The castle is managed by the Iran Cultural Heritage Organisation and a protected site .