it is the fourth-largest city in Iran, after Tehran, Mashhad, and Isfahan.
The earliest records of Karaj date back to 30th century BC. The city was developed under the rule of the Safavid and Qajar dynasties, and is home to historical buildings and memorials from those eras. Until the second half of the 20th century, it used to be known mainly as a summer resort. Today, it is a major industrial city, with factories producing sugar, textiles, wire, and alcohol.