Tehran, the capital of the Islamic Republic of Iran, is a case of unplanned urban development. About 12% of Iranians are Tehran dwellers, and geology plays a major role in their environment. The city is located in northern Iran in the foothills of the Alborz Mountains. Sediments underlying the city are composed of coarse (northern part of Tehran) to very fine (southern part of Tehran) sandstone, siltstone, and mudstone with interbeds of gravels and pebbles in various proportions up to a depth of 1600 m. The early settlers were attracted to the area because there were bountiful springs and kanats (or qanats, an underground channel with vertical access shafts used to transport water from an aquifer under a hill to the surface without the need for pumping). The inharmonious geomorphology has strongly influenced the local climate for Tehran, with northern portions of the city in the humid mountains and southern portions in the desert. As development and expansion of the urban area continue, there will be increasing demand for natural resources and services such as water supply and construction material, land-use changes, increasing pollution, and exposure to geological hazards. In this article, we use surface and subsurface geological data to highlight the geological constraints on sustainable urban growth and management.