Isfahan province consists of 52 rivers. They are small and temporary, with the exception of the Zāyanderud, which totals 405 km in length a basin area of 27,100 km2. Historians have recorded "Espahan", "Sepahan" or "Isfahan" initially as a defense and military base. The security and protection of the gradually increasing castles and fortifications, thereby, would provide the protection of residents nearby, therefore leading to the growth of large settlements nearby. These historical castles were "Atashgah", "Sarooyieh", "Tabarok", "Kohan Dej", and "Gard Dej". The oldest of these is "Ghal'eh Sefeed" and the grounds at "Tamijan" from prehistoric times. The historic village of Abyaneh, a nationwide attraction, also has Sassanid ruins and fire temples among other historical relics. During the 17th and 18th centuries, Isfahan province enjoyed high standards of prosperity as it became the capital of Safavid Persia. While the city of Sepahan (Esfahan) was their seat of monarchy, Kashan was their place of vacation and leisure. Isfahan province encompasses various sects today. The majority of the people in the province are Persian speakers, but Bakhtiari Lurs, Georgians, Armenians, Qashqais and Persian Jews also reside in the province. The official language of the province is Persian, though different ethnic groups and tribes abide by their own language such as Judeo-Persian, Armenian, Georgian, Qashqai Turkic or Bakhtiari Lurish. Isfahan province is noted for its reputed personalities such as writers, poets and other eminent figures who have been born and brought up or have lived in this territory. Several well-known Islamic Azad University campuses in Iran are located in the province: