Tehran is the capital city of Iran and the country's most populous city. It is situated in the northern part of the country. Tehran is one of the oldest cities in the world and is known for its diverse culture and rich history. It is Iran's economic, transportation, and cultural hub. Since ancient times, Tehran has played an influential role regionally and globally. The city is known for its mesmerizing blend of ancient architecture and modern high-rises. Some of the famous landmarks include the grand Golestan Palace, the bustling Grand Bazaar, and the impressive Milad Tower.

In Iran, the census is conducted every five years, with the last one being in 2016. According to this census, Tehran had a population of more than 9 million. The city is multicultural, hosting people from different ethnicities and backgrounds. Tehran is predominantly Muslim, with a significant number of Armenians, Zoroastrians, Jews, and Christians also living in the city. Tehran is home to many languages; although Persian is the official and most widely spoken language, other languages like Azerbaijani, Armenian, and English are also spoken. The Azadi Tower, one of Tehran's most iconic landmarks, was built in 1971 and has since been a symbol of the city. Tehran also houses the National Jewelry Museum, which holds the most expensive jewels in the world, collected over centuries.

The city of Tehran is governed by the Tehran City Council and the Mayor of Tehran. The council is elected by the public every four years, and it elects the mayor. The council is responsible for citywide policies and administration, while the Mayor of Tehran handles the executive responsibilities and oversees the municipal budget. On a district level, Tehran is divided into 22 municipal districts, each with its own mayor and council, responsible for local administration and services.

Tehran is the economic heart of Iran, contributing to about 30% of the country's GDP. It has a diverse economy with a large public sector. Some of the main industries include automotive, electrical, military weaponry, textiles, sugar, cement, and chemical. Tehran is also the country's leading hub for the telecommunications, electronics, and IT industries. Tehran Stock Exchange, which is one of the best performing exchanges in the world, is also located in this city.

Tehran has seen major growth and development in its infrastructure. The city has a comprehensive public transport system consisting of metro, bus, and taxi services. The Tehran Metro is one of the busiest in the Middle East, with several lines covering the city and its suburbs. The city also boasts numerous parks, libraries, and hospitals. In recent years, Tehran has made significant strides towards improving its digital infrastructure, with increased internet and mobile penetration and a growing tech startup ecosystem.