Kazakhstan, officially the Republic of Kazakhstan, is a landlocked country situated primarily in Central Asia, with a small portion of its territory extending into Eastern Europe. It borders Russia to the north and west, China to the east, Kyrgyzstan to the southeast, Uzbekistan to the south, and Turkmenistan to the southwest, and it has a coastline along the Caspian Sea. The capital is Astana, and Almaty, the country’s largest city and principal cultural and economic center, served as the capital until 1997. Kazakhstan is the world's ninth-largest country by land area and the largest landlocked country. Hilly plateaus and plains account for nearly half its vast territory, with lowlands composing another third; its southern and eastern frontiers are composed of mountainous regions. Kazakhstan has a population of 20.5 million and one of the lowest population densities in the world, with fewer than 8 people per square kilometre (21 people/mi2). Ethnic Kazakhs constitute a majority, while ethnic Russians form a significant minority. Officially secular, Kazakhstan is a Muslim-majority country with a sizeable Christian community. Kazakhstan has been inhabited since the Paleolithic era. In antiquity, various nomadic Iranian peoples such as the Saka, Massagetae, and Scythians dominated the territory, with the Achaemenid Persian Empire expanding towards the south.