Tehran is the country's capital and largest city, as well as its leading cultural and economic center. Iran is a major regional and middle power, exerting considerable influence in international energy security and the world economy through its large reserves of fossil fuels, which include the largest <answer>natural gas</answer> supply in the world and the fourth-largest proven oil reserves. Iran's rich cultural legacy is reflected in part by its 19 UNESCO World Heritage Sites, the fourth-largest number in Asia and 12th-largest in the world.
What resource does Iran have the largest supply of in the world?
natural gas