Karachi also called as "the City which never sleeps or the city of lights Uroos ul Bilaad" and "City of the Quaid", is capital of province Sindh and capital of Pakistan until Islamabad was constructed as a capital as well as the largest and most populous metropolitan city of Pakistan covering an area of 3257 sq Km having a density of more than 6000 people per sq km making the the 2nd-largest city in the world by population within city limits, the 7th largest urban agglomeration in the world and the largest city in the Muslim world and the main seaport and financial centre of the country.