Arba 'a Rukun Mosque is one of the oldest Islamic places of worship in the capital . It was built circa 667 ( 1268 / 9 AD ) , concurrently with the Fakr ad @-@ Din Mosque . Arba 'a Rukun 's mihrab contain an inscription dated from the same year , which commemorate the masjid 's late founder , Khusra ibn Mubarak al @-@ Shirazi ( Khusrau ibn Muhammed ) .