Geographically, Iran is for the most part a plateau at an average altitude of about a thousand metres; the terrain—the near-jungle conditions of the Caspian littoral excepted—is arid semi-desert and the typical landscape one of limestone mountain ranges between which lie flat plains. It is bordered by Iraq, Turkey, the U.S.S.R., the Caspian Sea, Afghanistan, Pakistan and the Persian Gulf. Except during spring the vegetation in most areas is sun-shrivelled on the bare treeless earth; after five months of burning heat the winter rainfall washes off the topsoil, and river-beds, dry throughout the summer, overflow with muddy torrents. Although the soil is dry and powdery there are abundant watercourses below the surface and with irrigation the land is very productive. The country has great mineral resources; apart from the oil-fields they are un-exploited due to lack of coal and road and rail communications. The people are mainly feudal villagers or nomadic tribesfolk but Tehran is a modern city of a million population and the provincial capitals are also semi-Westernized.