Korea is a mountainous peninsula surrounded by the sea on three sides. It shares its northern borders with China and Russia, and its closest southern neighbor is Japan, which lies across a narrow strait. The Korean peninsula measures approximately six hundred miles from its northern tip to its southern end.
The people of Korea have governed themselves since ancient times, except during the period of Japanese colonial rule (1910–1945). Koreans speak a single language and regard themselves as homogeneous, although some intermixing has taken place with the peoples of Northeast Asia, Mongolia, China, and Japan.