Karaj

The area around Karaj has been inhabited for thousands of years, as shown by the Bronze Age cemetery of Tepe Khurvin and the Iron Age site of Kalak on the left bank of the Karaj River. Before the 20th century Karaj was mainly a stage on the road between Tehran and Qazvin. In the Safavid period a large caravanserai and a stone bridge were built there; the bridge remained the main crossing of the Karaj River until the late 20th century. In 1810 the Qajar prince Soleyman Mirza, a former governor of Kermanshah, built the Soleymaniyeh Palace at Karaj as a summer residence. The palace had four towers and was surrounded by walls and gardens, and its reception room had paintings by Abdallah Khan Naqqashbashi. By 1860 it was described as abandoned and used only as a shelter for travellers; Naser al-Din Shah Qajar later restored it. …

Karaj lies on a broad plain with gentle hills at the foot of the Alborz, north of the Shahriar agricultural plain and east of the Savojbolagh and Hashtgerd plains. The Karaj River flows through the city from the mountains to the north. The Tehran–Qazvin highway, the railway and the metro line divide the city into northern and southern parts. The traditional centre is around Karaj Square, west of the Karaj River and the old bridge. The northern part includes Hesarak, the site of the Razi Vaccine and Serum Research Institute, Gohardasht (officially renamed Rajaei Shahr) and Shahrak-e Azimiyeh. The southern part includes the planned district of Mehrshahr; Kalak lies along the river. The agricultural area of Meshkin Dasht lies outside the municipal boundary. In 1997 the municipality was divided into ten districts. …

Karaj is a major industrial city, with factories producing sugar, textiles and wire among other goods. Encyclopaedia Iranica, citing a study by Korby, describes its industrial zone as the largest in Iran. Its economy also benefits from its position on the main routes from Tehran to the north-west and to the Caspian coast. The Payam special economic zone, around Payam International Airport, was established for air cargo, postal transport, cold storage and packing services and for exports of perishable and time-sensitive goods.

Karaj is on the main railway between Tehran and Qazvin. Line 5 of the Tehran Metro, a suburban line, connects Karaj with Tehran and has operated since the late 1990s. The Karaj Urban Railway Organization was established on 21 December 2001 to build a separate Karaj Metro. Its first line, Line 2, opened for limited service on 27 February 2023 between Golshahr and Ayatollah Taleqani, and was extended to Shahid Soltani on 6 September 2025. When complete, Line 2 is planned to be 27 km (17 mi) long with 23 stations. In the city's planned network, the existing Tehran Metro Line 5 corridor counts as Line 1. The main roads are the Tehran–Karaj Freeway, the Karaj Special Road and the old Karaj road (Fath Highway). The Tehran–Karaj Freeway is one of the busiest roads in Iran, with an annual average daily traffic of 217,084 vehicles. In west Tehran it connects with the Bakeri Expressway. …

At the 2006 census the city had 1,377,450 inhabitants in 385,955 households, when it was part of Tehran province. The 2016 census recorded 1,592,492 people in 508,420 households, by which time the county had become part of the new Alborz province. Karaj County as a whole had 1,973,470 inhabitants in 2016. Karaj is one of Iran's main destinations for internal migration, and Encyclopaedia Iranica describes its population as ethnically, culturally and economically heterogeneous. Most residents are Persians; Azerbaijanis form the second-largest group, and there are also Kurds, Lurs, Gilaks and Mazanderanis.