Ghahestan or Koohestan ( mountainside) region is surrounded by desert from the south of Neyshaboor to Sistan and has semi-arid temperate or mountainous climate. Marco Polo in his travel account has named this city as "Tonokayn". This name is a combination of two large cities of this state i.e. "Toon" and "Ghayen".
Ghahestan state was place of refuge for Zoroastrians simultaneous with arrival of Arabs. In Salijooghian period it was a place for Esmailieh disciples who constructed strong castles for defense.
The important historical sites of the city are:
Khading cave.
Boozarjomehr mausoleum,
Sheikh Abolfakher grave.
Jame’ Mosque.