Greater Isfahan Metropolitan Area is a metropolitan region in Isfahan Province, central Iran. This region, although not having any official designation and recognition yet, is the second biggest one in Iran, behind the capital city Tehran (Greater Tehran). The overall region has a population of over 3,500,000 and extends along Zayandeh Rud, the main river axis through the province, and also along the northern-southern axis of the city, plus a western axis towards Lorestan Province.