Dareh Shahr is one of the important and ancient cities of Ilam Province. It is located in southeastern Ilam 840 kilometers from Tehran between new Dareh Shahr and the Bahman Abad Village. Holding vast fertile lands, different and rich water resources, rich pastures, dense forests, Dareh Shahr offers a mild climate and is situated in a relatively wide valley with many historical ascent and descents.Attacks of Arabs and Assyrians caused destruction of the city. Its forgotten and extinct fire-temple is still standing. In ancient times Elamites governed the Lorestan mountains and constructed several strong buildings. Dareh Shahr was the first Elamite city attacked and destroyed by Assyrians in addition to the massacre of people. In Simareh Valley the remains of the Sassanid monuments are still present; hence Dareh Shahr might have been a thriving city in the Sassanid and the Parthian periods.Furthermore some foreign experts call the unearthed city as the second and lost capital of the 'Selukis' while some Iranian archeologists believe that the monuments are part of the state of 'Sirvan'. Referencing some resources and texts, Dareh Shahr may be the same as Mehr Jaan Ghazagh, Saabzaan, Simareh or the city of Khosrow Parviz in the late Sassanid period completely leveled to earth from an earthquake in the years 248 and 344 A.H.