South Korea is a country that could be considered as an island, as the only border existing in the peninsula is probably the most hermetic in the world. In the meantime, the hinterland is composed of discontinuous mountains and rivers. Cities have to be concentrated in very small areas while the last decades have been marked by a remarkably fast growing of the economy.
Today, Seoul and its surrounding cities arerepresentating half of the population of South Korea. Large industrial complexes, mainly controlled by the Chaebol (the biggest south korean private conglomerates), are employing hundreds of thousands of koreans, who now live in residential districts, composed of high skyscrapers. These disctricts are often located nearby main highways, that can be noisy to residents. Therefore, soundproofs walls are often built along large roads, and can even sometimes be composed of a full soundproof tunnel, covering the whole highway.