South Korea, officially the Republic of Korea (or ROK) an often referred to as Korea (Korean: 대한민국, IPA: [tɛː.han.min.ɡuk̚], Hanja: 大韓民國), listen (help·info)) is a presidential republic in East Asia, occupying the southern half of the Korean Peninsula. Also known as the "Land of the Morning Calm", it is bordered by China to the west, Japan to the east and North Korea to the north, with which it was united until 1945. Its capital and largest city is Seoul, the world's second largest metropolitan city.