South Korea occupies the southern portion of the Korean Peninsula, spanning 100,210 square kilometers. The peninsula extends southward from the Asian continental landmass between 33°N and 43°N latitude, with South Korea controlling territory from the Demilitarized Zone at approximately the 38th parallel north to the Korea Strait. The country's maximum north-south distance measures approximately 450 kilometers, while the east-west width varies from 175 to 300 kilometers. Three bodies of water define the national boundaries: the Yellow Sea along the western coast, the East Sea along the eastern coast, and the Korea Strait separating the peninsula from Japan to the south. The coastline extends 2,413 kilometers when excluding islands, but reaches approximately 8,640 kilometers when accounting for the roughly 3,000 islands under South Korean jurisdiction.
Mountain ranges dominate 70 percent of South Korea's landmass. The Taebaek Mountains form the primary north-south spine running parallel to the eastern coast, originating near the DMZ and extending approximately 500 kilometers southward through Gangwon Province into North Gyeongsang Province. This range creates an asymmetrical geography where the eastern slope descends steeply to the East Sea across 30 to 50 kilometers, while the western slope grades gradually across 200 kilometers toward the Yellow Sea. The highest peak in the Taebaek range within South Korean territory reaches 1,708 meters at Seoraksan. The Sobaek Mountains branch southwestward from the Taebaek range near the city of Yeongju, extending approximately 350 kilometers through the interior of the peninsula and reaching elevations between 1,000 and 1,400 meters. These two mountain systems create the fundamental drainage divide that determines river flow patterns across the peninsula.
Hallasan stands at 1,947 meters on Jeju Island as South Korea's highest point. This shield volcano occupies the center of Jeju Island, which lies 85 kilometers south of the Korean Peninsula across the Jeju Strait. Hallasan's summit crater, called Baengnokdam, measures 400 meters in diameter and contains a shallow lake approximately 100 meters across during wet seasons. The mountain's base diameter spans 30 kilometers, and its slopes contain approximately 360 parasitic cones called oreums. Geological surveys date Hallasan's formation to volcanic activity beginning 1.8 million years ago, with the most recent eruption occurring in 1007 CE according to the Goryeosa historical record. The mountain's elevation creates distinct vegetation zones: subtropical broadleaf forest below 600 meters, temperate broadleaf forest from 600 to 1,400 meters, coniferous forest from 1,400 to 1,800 meters, and sub-alpine dwarf vegetation above 1,800 meters. Snow typically covers the summit from November through April, with annual snowfall at the peak averaging 280 centimeters.
Jirisan, located where North Jeolla, South Jeolla, and South Gyeongsang provinces converge, rises to 1,915 meters at Cheonwangbong peak, making it the highest point on mainland South Korea. The massif extends 40 kilometers east to west and 32 kilometers north to south, encompassing 483 square kilometers within Jirisan National Park boundaries established in 1967 as South Korea's first national park. The mountain contains three major peaks: Cheonwangbong at 1,915 meters, Banyabong at 1,732 meters, and Nogodan at 1,507 meters. Ten major valleys radiate from the central ridge, carved by streams that collectively feed the Seomjin River to the south and tributaries of the Nakdong River to the east. The name Jirisan translates approximately as "mountain of the odd and wise people," referenced in texts dating to the Silla period, when the peaks served as retreat locations for Buddhist monks and Taoist practitioners. Winter temperatures at Cheonwangbong average minus 10 degrees Celsius in January, while the summit receives approximately 3,000 millimeters of annual precipitation, roughly double the Korean peninsula average.
Seoraksan rises to 1,708 meters at Daecheongbong peak in Gangwon Province, 170 kilometers northeast of Seoul. The mountain's name derives from "seol-ak," meaning "snowy peak," reflecting the rock's appearance during ten months when snow typically persists at elevation. The massif divides into three sections: Outer Seorak on the eastern slope facing the East Sea, Inner Seorak on the western slope, and South Seorak extending toward the city of Yangyang. Granite formations dominate the geology, with spires and cliffs composed of Mesozoic granite intruded 100 to 150 million years ago. Gwongeumseong, a rock fortress at 800 meters elevation, contains wall remnants from fortifications constructed during the Goryeo Dynasty between 1253 and 1258 CE during Mongol invasions. The Seoraksan region receives 1,300 to 1,500 millimeters of annual precipitation, with fog occurring on average 200 days per year at elevations above 1,000 meters. Cable car infrastructure installed in 1970 transports visitors from the entrance at 310 meters elevation to Gwongeumseong at 800 meters across a horizontal distance of 1,100 meters.
The Demilitarized Zone stretches 250 kilometers across the Korean Peninsula at the 38th parallel north, varying in width from 2 to 4 kilometers. The Military Demarcation Line bisects this zone, with South Korean control extending 2 kilometers south of this line and North Korean control extending 2 kilometers north. The Armistice Agreement signed on July 27, 1953, at Panmunjom established these boundaries. The DMZ's western terminus begins at the Yellow Sea near Gorangpo, passing through elevations ranging from sea level to 1,120 meters at Mount Myohyang near the eastern terminus at the East Sea. Restricted human access since 1953 has allowed secondary forest succession across 60 percent of the DMZ area, with additional wetland habitats occupying former rice paddies. The Civilian Control Zone extends an additional 5 to 20 kilometers south of the DMZ's southern boundary, creating a combined restricted area encompassing approximately 1,560 square kilometers in South Korea. Elevation changes across the DMZ create distinct ecosystems: coastal wetlands and estuaries in the west at elevations below 10 meters, central lowlands and river valleys from 10 to 100 meters, and forested mountains in the east reaching above 1,000 meters.
Four major river systems drain the Korean Peninsula south of the DMZ. The Han River, at 514 kilometers in length, drains 26,219 square kilometers including the Seoul metropolitan area before emptying into the Yellow Sea near Incheon. The river originates from two sources in the Taebaek Mountains: the North Han River beginning at 1,410 meters elevation near Mount Geomryong, and the South Han River beginning at 1,152 meters elevation near Taebaek city. These branches converge at Yangpyeong, 40 kilometers east of Seoul, where the combined flow averages 680 cubic meters per second. The Nakdong River extends 525 kilometers, making it South Korea's longest river, draining 23,817 square kilometers before reaching the Korea Strait near Busan. Originating at 1,241 meters elevation on the eastern slope of the Taebaek Mountains near Taebaek city, the Nakdong flows south through interior valleys before turning eastward through Gyeongsang provinces. The Geum River measures 401 kilometers, draining 9,912 square kilometers in the central western region before emptying into the Yellow Sea near Gunsan. The Yeongsan River extends 136 kilometers through southwestern provinces, draining 3,467 square kilometers before reaching the Yellow Sea near Mokpo.
Jeju Island rises from the continental shelf approximately 90 kilometers south of the Korean Peninsula across the Jeju Strait. The island measures 73 kilometers east to west and 41 kilometers north to south, covering 1,849 square kilometers as South Korea's largest island. Volcanic basalt underlies the entire island, formed through eruptions occurring between 1.8 million and 1,000 years ago. Seongsan Ilchulbong, a tuff cone on the eastern coast, rises 182 meters above sea level with a crater measuring 600 meters in diameter and 90 meters deep. This formation emerged from underwater volcanic eruptions approximately 5,000 years ago, later connecting to the main island through sediment deposition. Manjanggul Cave extends 7,416 meters as one of the world's longest lava tubes, formed when molten lava flowed beneath solidified crust during eruptions 250,000 to 300,000 years ago. The tube maintains widths from 2 to 23 meters and heights from 2 to 30 meters, with a 1,000-meter section open for visits. The Geomunoreum Lava Tube System encompasses multiple tubes and cones formed during eruptions 100,000 to 300,000 years ago, including Bengdwigul at 4,481 meters length and Manjanggul.
Ulleungdo Island lies 130 kilometers east of the Korean Peninsula in the East Sea, covering 72.9 square kilometers. The island formed from volcanic eruptions beginning 2.5 million years ago, with the most recent volcanic activity occurring approximately 5,000 years ago. Seonginbong peak rises 984 meters at the island's center, surrounded by steep cliffs that descend to the coastline across distances of 3 to 5 kilometers. The island's circular shape spans approximately 10 kilometers in diameter. No natural harbors exist due to the steep submarine slopes, requiring specialized ferry approaches at Dodong and Jeodong ports. Dokdo Islands lie 87 kilometers east of Ulleungdo, comprising two main islets and 89 smaller rocks covering a total area of 0.187 square kilometers. The western islet measures 200 meters by 140 meters, reaching 168.5 meters elevation, while the eastern islet measures 250 meters by 180 meters, reaching 98.6 meters elevation. These volcanic formations emerged from underwater eruptions 4.6 million years ago, with basalt and tuff composing the primary geology.
The Yellow Sea coastline along South Korea's western border features extensive tidal flats measuring up to 6 kilometers in width. The maximum tidal range reaches 9.6 meters at Incheon during spring tides, ranking among the world's highest tidal ranges. The Saemangeum Seawall, completed in 2010, spans 33.9 kilometers as the world's longest sea dike, enclosing 400 square kilometers of former tidal flats in North Jeolla Province. The East Sea coastline presents steep cliffs and narrow beaches due to the adjacent Taebaek Mountains. The continental shelf extends only 10 to 30 kilometers offshore along the eastern coast before dropping to depths exceeding 1,000 meters, compared to the Yellow Sea's gradual slope where 200-meter depth contours lie 300 kilometers from shore. The Korea Strait between South Korea and Japan maintains depths between 100 and 200 meters across its 180-kilometer width, narrowing to 50 kilometers at the Tsushima Strait between Busan and Tsushima Island.
Suncheon Bay Wetland Reserve protects 28 square kilometers of tidal flats and reed beds in South Jeolla Province where the Dong stream meets the bay. Reed beds cover 5.4 square kilometers, with individual Phragmites australis stems reaching 2 to 4 meters height. The site serves as stopover habitat for 140,000 to 200,000 migratory birds during autumn migration periods, documented through annual surveys conducted since 1996. Upo Wetland in Gyeongsang Province encompasses 2.31 square kilometers across four connected freshwater wetlands: Upo, Mokpo, Sajipo, and Jjokjipo. These wetlands formed approximately 140 million years ago when tectonic activity created depressions that filled with water from the Nakdong River. Water depths range from 0.5 to 1.5 meters during summer months, decreasing to 0.3 to 1.0 meters during winter dry season. Junam Reservoir, constructed in 1920 for irrigation in Gyeongsang Province, covers 2.4 square kilometers and hosts 20,000 to 30,000 wintering waterfowl annually, including white-naped cranes counted at 200 to 400 individuals during winter surveys.
The Baekdudaegan ridge system extends along the Taebaek and Sobaek mountain ranges for approximately 1,400 kilometers from Mount Baekdu on the Chinese-North Korean border to Jirisan in South Korea. This traditional geographic concept, documented in the Sinjung Dongguk Yeoji Seungnam geographic text from 1530 CE, identified the mountain spine as the peninsula's primary geographic feature influencing water flow, climate, and settlement patterns. Within South Korea, the Baekdudaegan extends approximately 700 kilometers, connecting peaks above 1,000 meters elevation through continuous ridgelines. The concept influenced Joseon Dynasty practices including grave site selection, city planning, and infrastructure routing that avoided crossing the main ridge. Contemporary conservation initiatives designated a 263-kilometer section from the DMZ to Jirisan as a protected corridor in 2005, restricting development within 500 meters of the ridgeline.
Bukhansan rises to 836.5 meters at Baegundae peak within Seoul's municipal boundaries, 13 kilometers north of the Han River. The mountain's granite peaks emerged from Mesozoic intrusions approximately 150 million years ago. Bukhansan National Park, established in 1983, covers 76.9 square kilometers despite being South Korea's smallest national park by area, yet receives 5 to 6 million visitors annually, ranking it among the world's most visited national parks per unit area. Fortress walls extending 9.5 kilometers encircle the three main peaks at elevations between 400 and 800 meters, constructed in 1711 during the Joseon Dynasty using 100,000 workers over 100 days according to the Sukjong Sillok royal annals. The walls incorporated 13 gates and 16 command posts. Rock climbing routes numbering over 100 follow crack systems and face climbs on granite walls ranging from 30 to 200 meters height, with route development beginning in the 1970s.
Dadohaehaesang National Park protects 2,344 square kilometers across marine and island areas in South Jeolla Province, established in 1981 as South Korea's largest national park by total area. The park encompasses approximately 1,700 islands ranging from exposed rocks to islands covering several square kilometers. Hongdo Island, located 115 kilometers from the mainland port of Mokpo, covers 6.5 square kilometers with coastal cliffs reaching 250 meters height composed of Precambrian metamorphic rock aged approximately 1 billion years. Heuksando Island, 96 kilometers from Mokpo, covers 19.7 square kilometers and rises to 227 meters elevation at Sangrakbong peak. The archipelago experiences strong tidal currents reaching 5 to 7 knots during spring tides, creating nutrient upwelling that supports marine biodiversity. Water temperatures range from 6 to 8 degrees Celsius in February to 24 to 26 degrees Celsius in August, measured at 10-meter depth.
The East Sea coastline features numerous lagoons formed when sand bars enclosed coastal inlets. Gyeongpo Lake near Gangneung covers 1.02 square kilometers with maximum depth of 2.5 meters, separated from the East Sea by a 250-meter-wide sand bar. Hwajinpo Lake in northern Gangwon Province covers 2.3 square kilometers, lying 500 meters inland from the coast behind a sand bar 300 to 500 meters wide. These lagoons transitioned from saltwater to brackish conditions over centuries as sediment deposition reduced tidal exchange. Sokcho city developed around Cheongchoho Lake, a lagoon covering 1.24 square kilometers that maintains connection to the East Sea through a 50-meter-wide channel dredged for fishing vessel access.