Afghanistan, officially the Islamic Republic of Afghanistan, is a landlocked country in South Asia. Afghanistan is bordered by Pakistan to the east and south; Iran to the west; Turkmenistan, Uzbekistan, and Tajikistan to the north; and China to the northeast. Occupying 652,000 square kilometers (252,000 sq mi), it is a mountainous country with plains in the north and southwest. Kabul is the capital and largest city. The population is around 32 million, mostly composed of ethnic Pashtuns, Tajiks, Hazaras and Uzbeks. Human habitation in Afghanistan dates back to the Middle Paleolithic Era, and the country's strategic location along the Silk Road connected it to the cultures of the Middle East and other parts of Asia. Afghanistan is a unitary presidential Islamic republic. The country has high levels of terrorism, poverty, child malnutrition, and corruption.