Hyderabad is the capital of the southern Indian state of Telangana and de jure capital of Andhra Pradesh. Occupying 650 square kilometres (250 sq mi) along the banks of the Musi River, it has a population of about 6.7 million and a metropolitan population of about 7.75 million, making it the fourth most populous city and sixth most populous urban agglomeration in India. At an average altitude of 542 metres (1,778 ft), much of Hyderabad is situated on hilly terrain around artificial lakes, including Hussain Sagar—predating the city’s founding—north of the city centre. Hyderabad emerged as the foremost centre of culture in India with the decline of the Mughal Empire in the mid-19th century, with artists migrating to the city from the rest of the Indian subcontinent. The Telugu film industry based in the city is the country’s second-largest producer of motion pictures. Hyderabad was historically known as a pearl and diamond trading centre, and it continues to be known as the “City of Pearls”.