Afghanistan is a landlocked country in South Asia bordering China, Pakistan, Iran, Tajikistan, Uzbekistan and Turkmenistan. Spanning over 652,000 square miles, the majority-Muslim country's geography can be divided into the highlands, the northern plains and the southwestern plateau. Mountains are Afghanistan's dominant geographic feature, with the Hindu Kush range running at a southwestern angle and roughly dividing the country in half. The four most important cities are the capital Kabul in the east, Kandahar in the south, Herat in the west, and Mazar-i-Sharif in the north. Because of its location, the country functions as a bridge between energy-rich Central Asia and energy-deficient South Asia. Afghanistan's primary geographic challenge is resisting the intervention of outside powers while also maintaining authority over a mostly rural society spread across a rugged landscape. Afghanistan's location at the crossroads of the Middle East, Central Asia and the Indian subcontinent has historically invited external actors, resulting in a country containing diverse languages, cultures and ethnicities. Indeed, Afghan society includes significant populations of Pashtun, Tajiks, Turkmens, Uzbeks and Hazaras. Each of these groups share populations in a neighboring country, encouraging external involvement. The borders of modern-day Afghanistan were drawn during the 19th century to carve out a space between the British and Russian empires. Afghanistan's most contentious boundary is with Pakistan and is called the Durand Line. Afghanistan disputes the border, claiming that its true boundary should absorb Pakistan's Pashtun-majority region. This fuels the antagonism between the two countries and plays a role in Afghanistan's broader challenge of asserting sovereignty as outside actors try to advance their own interests.