THE CAPITAL of modern Iran, Tehran is 1 of the largest cities of the world with a metropolitan population of 15 million people. Located on the northernmost limit of the central Iranian plateau, the city is appropriately 3,750 foot (1,143 meter) above sea level. To the northeast are the Iranian uplands and the snowcapped Mt. Demovend, legendary home to Zoroaster. The city’s climate is fairly temperate with average summertime temperatures in the upper 70s degrees F (upper 20s degrees C), but close to 32 degrees F (0 degrees C) in the winter. Its rainy season lasts between November and May. Unlike other Iranian cities, Tehran is not of ancient origin; it is too far removed from the centers of Iranian civilization to the south and west. Its earliest history dates to the 9th century C.E., when Tehran was a small village marked by subterranean dwellings. It remained such a town sitting astride the caravan route that ran across the plateau between Central Asia and Mesopotamia until 1220 C.E., when invading Mongols sacked and completely destroyed the larger nearby city of Ray. In 1553, the ruling Safavid kingdom made Tehran a second capital, using it as a resort until the decline of the dynasty. Subsequently, the city was sacked by an Afghan incursion that left the city almost deserted. Tehran recovered but remained of secondary importance until Agha Muhammad Khan, the founder of the Qajar dynasty, occupied the city, and because it was close to his tribal lands, he made it his capital in 1788. The Qajar kings enriched the city with palaces, markets, and residences, and Tehran flourished. By the end of the 19th century, city-planning, improvement projects, which included the Sepahsalar mosque, and the first telegraph transformed Tehran into a modern metropolis.