Tehran ), sometimes spelled Teheran, is the capital of Iran (I.R.) and Tehran Province. With a population of 8,429,807; it is also Iran's largest urban area and city, one of the largest cities in Western Asia, and is the world's 19th largest city.In the 20th century, Tehran was subject to mass-migration of people from all around Iran. However it is suggested that 5 million should migrate out of the city. The city is home to many historic mosques, churches, synagogues and Zoroastrian fire temples. Contemporary Tehran is a modern city featuring many tall structures, of which the Azadi (Freedom) Tower and the Milad Tower have come to be symbols of Tehran itself. Internationally Tehran was in 2008, the least expensive capital in the world and only the second least expensive city globally based on Cost-of-living index, in addition to presenting the best value for money in the world. Furthermore globally it stands 19th by city population, 56th by the size of its GDP and 29th by the population of its metropolitan area. Due to long history of Iran, there have been many instances of capital city relocations over the ages and Tehran, currently is the 32nd national capital of Iran. The native language of the city is the Tehrani dialect of Persian, with 98% nativespeakers and the majority of people in Tehran identify as Persians. In pre-Islamic and early Islamic times, Tehran was called Ray which in the Avesta occurs in the form of Ragha.