Rawalpindi, colloquially known as Pindi, is the capital city of Rawalpindi Division located in the Punjab province of Pakistan. Rawalpindi is the fourth-largest city proper in Pakistan after Karachi, Lahore and Faisalabad respectively while the larger Islamabad-Rawalpindi metropolitan area is the country's third largest metropolitan area. Rawalpindi is adjacent to Pakistan's capital of Islamabad, and the two are jointly known as the "twin cities" on account of strong social and economic links between the cities