South Korea occupies the southern half of the Korea Peninsula, which extends about 1,000 km (about 620 mi) southward from northeastern China. The total area of South Korea is 99,268 sq km (38,328 sq mi), including about 3,000 islands. South Korea is a mountainous country. Lowlands, located primarily in the west and southeast, constitute only 30 percent of the total land area. South Korea can be divided into three general regions: an eastern region of high mountain ranges and narrow coastal plains; a western region of broad coastal plains, river basins, and rolling hills; and a southern region, where a maze of mountains and valleys in the west contrasts with the broad basin of the Nakdong River in the southeast.

Halla-san, an extinct volcano that forms Jeju Island, is the country’s highest point at 1,950 m (6,398 ft). Jeju Island is located about 100 km (about 60 mi) off the southern coast of South Korea. It is the country’s largest island, with an area of 1,845 sq km (712 sq mi).

The Taebaek range forms the country’s principal mountain system. It extends in a generally north-south direction parallel to the eastern coast. Four other mountain ranges extend from the Taebaek range, including the Sobaek range, the country’s second largest mountain system. The Sobaek range branches southwestward from the Taebaek range, dividing the southern part of the country. The highest peak of the mainland, Jiri-san (1,915 m/6,283 ft), rises in the southern portion of the Sobaek range. The mountain ranges of the mainland formed through geologic folding, in contrast to the volcanic origin of Halla-san. The mainland has no volcanic activity, and earthquakes are rare.