Iran is one of the world's most mountainous countries. Its mountains have helped to shape both the political and the economic history of the country for several centuries. The mountains enclose several broad basins, or plateaus, on which major agricultural and urban settlements are located. Until the twentieth century, when major highways and railroads were constructed through the mountains to connect the population centers, these basins tended to be relatively isolated from one another. Typically, one major town dominated each basin, and there were complex economic relationships between the town and the hundreds of villages that surrounded it. In the higher elevations of the mountains rimming the basins, tribally organized groups practiced transhumance, moving with their herds of sheep and goats between traditionally established summer and winter pastures. There are no major river systems in the country, and historically transportation was by means of caravans that followed routes traversing gaps and passes in the mountains. The mountains also impeded easy access to the Persian Gulf and the Caspian Sea.

With an area of 1,648,000 square kilometers, Iran ranks sixteenth in size among the countries of the world. Iran is about one-fifth the size of the continental United States, or slightly larger than the combined area of the contiguous states of California, Arizona, Nevada, Oregon, Washington, and Idaho.

Located in southwestern Asia, Iran shares its entire northern border with the Soviet Union. This border extends for more then 2,000 kilometers, including nearly 650 kilometers of water along the southern shore of the Caspian Sea. Iran's western borders are with Turkey in the north and Iraq in the south, terminating at the Shatt al Arab (which Iranians call the Arvand Rud). The Persian Gulf and Gulf of Oman littorals form the entire 1,770-kilometer southern border. To the east lie Afghanistan on the north and Pakistan on the south. Iran's diagonal distance from Azarbaijan in the northwest to Baluchestan va Sistan in the southeast is approximately 2,333 kilometers.

Data as of December 1987