Karachi is the capital of the province of Sindh, as well as the largest and most populous metropolitan city of Pakistan. It is the 2nd-largest city in the world by population. It is also the main seaport and financial centre of the country. Karachi is also known as City of Lights mainly due to city's night life, for which it is famous as the city which never sleeps. Karachi metro has an estimated population of over 23.5 million people as of 2013, and area of approximately 3527km2, resulting in a density of more than 6,000 people per square kilometre .Karachi is the 7th largest urban agglomeration in the world and the largest city in the Muslim world. It is Pakistan's centre of banking, industry, economic activity and trade and is home to Pakistan's largest corporations, including those involved in textiles, shipping, automotive industry, entertainment, the arts, fashion, advertising, publishing, software development and medical research. The city is a hub of higher education in South Asia and the Muslim world.