South Korea, officially the Republic of Korea, occupies the southern portion of the Korean Peninsula in East Asia. It is bordered by North Korea to the north, with the heavily fortified Korean Demilitarized Zone (DMZ) separating the two. Seoul, the capital, is a massive metropolis and one of the world's most tech-savvy cities. South Korea's geography is largely mountainous, with only about 30% of the land being flat enough for cultivation or urban development. The coastline is dotted with thousands of small islands, the largest being Jeju Island, a popular volcanic tourist destination. South Korea has a temperate climate with four distinct seasons. The country underwent rapid economic development, known as the 'Miracle on the Han River,' to become a global leader in electronics, automobiles, and popular culture (Hallyu). It is one of the most urbanized and densely populated countries in the world.