Islamabad is the capital city of Pakistan. Located within the Islamabad Capital Territory, the population of the city has grown from 95,940 in 1951 to 805,235 as of 1998 making it the ninth largest city in the country. According to a 2012 estimate by the Census Department, the population of Islamabad including its surrounding territory has increased to 2 million and together with its neighbouring twin city of Rawalpindi, the greater Islamabad-Rawalpindi metropolitan area is the third largest conurbation in Pakistan with a population of over 4.5 million inhabitants. Since its foundation, Islamabad has attracted people from all over Pakistan, making it one of the most cosmopolitan and urbanised cities of Pakistan. As the capital, Islamabad is the seat of the Government of Pakistan; the Presidential Palace is also located here. Islamabad is home to the Pakistan Monument, which is one of the two national monuments of Pakistan. Islamabad is known as a clean, calm and green city. It hosts a large number of diplomats, politicians and government employees.Islamabad is a modern, planned and maintained city located in the Pothohar Plateau in the northeastern part of the country, within the Islamabad Capital Territory. The region has historically been a part of the crossroads of Punjab and Khyber Pakhtunkhwa with the Margalla Pass acting as the gateway between the two regions. The city was built during the 1960s to replace Karachi as Pakistan's capital. Islamabad is a well-organised international city divided into several different sectors and zones. It is regarded as the most developed city in Pakistan and is ranked as a Gamma+ world city. The city is home to the Faisal Mosque, the largest mosque in South Asia and the fourth largest mosque in the world.Islamabad has the highest literacy rate in Pakistan. There are 16 recognised universities in Islamabad, including some of the top-ranked universities in Pakistan: Air University, Quaid-i-Azam University, Pakistan Institute of Engineering & Applied Sciences, and National University of Sciences and Technology. Allama Iqbal Open University in Islamabad is one of the world's largest universities by enrolment. Islamabad has the lowest infant mortality rate in the country at 38 deaths per thousand as compared to the national average of 78 deaths per thousand. The Pakistan Institute of Medical Sciences hospital in Islamabad is one of the largest hospitals in Pakistan.