This article compares past and present urban planning through the examples of Sangyeongseong and Sejong City in the Balhae region, and discusses the importance of urban engineering and the concept of smart cities. It explains that urban engineering is leading the way for the development of future cities, providing solutions for environmental protection, efficient land use, and social cohesion.

The development of urban engineering through the lens of Balhae Sangyeongseong Fortress and Sejong City

You may not be familiar with the name Sangyeongseong, but you may be familiar with the country of Balhae, which was founded by King Daejayong. It was the third capital of Balhae and enjoyed a period of cultural prosperity for about 160 years. Sanggyeongseong is laid out in a grid of main arterial roads centred around the inner city, with Jujak-daero in the centre. Starting from the southern gate of Hwangseong Fortress, Jujak-daero is a huge road that is 2.2 kilometres long from north to south and 110 metres wide.
There are several reasons why Balhae built such a large road in Shangjing City. The first reason was to facilitate the movement of supplies in preparation for the Ansha Rebellion in the mid-Tang Dynasty, and the second was to symbolise the strength of the royal power by creating a boulevard centred on the palace.
A city designed to fulfil a specific purpose is called a ‘planned city’. Planned cities are different from traditional cities, which developed naturally based on the accumulation of surplus production. Whereas traditional cities gradually grew in size based on economic affordability, planned cities are intentionally designed for the welfare and public well-being of their inhabitants by efficiently arranging urban functions such as transport, housing, sanitation, security, and administration. Planned cities as we know them today include Changwon and Ilsan, and more recently, Sejong Special Self-Governing City has gained attention as a prime example of such a city.
Sejong City is an administrative centre that aims to address the adverse effects of population concentration in the metropolitan area and strengthen the country’s balanced development and competitiveness. So why did Sejong City choose a grid road structure like Jujak-daero in Sangyeong-si, Balhae? In fact, grid-like roads such as Jujak-daero have many intersections, which can cause traffic congestion, and the expansion of roads can cause environmental damage. In addition, grid-style roads are not efficient because they lack a sense of unity among residents and are not well connected to the land. Considering the goals of Sejong City, grid roads are not suitable.

Planned cities and urban engineering

Planned cities are not just about transport and housing, they are designed to solve society-wide problems and lead to sustainable development in the future. Urban engineering plays an important role in this. Urban engineering is a discipline that helps cities organise and operate efficiently in a variety of areas, including transport, housing, environment, security, and administration. The discipline has provided practical answers to many of the social and environmental problems that have arisen as a result of population growth and rapid urbanisation.
More than just designing buildings and roads, urban engineering is key to creating sustainable cities and environments. Whether it’s reducing air pollution by streamlining transport systems or improving the quality of life for citizens by providing adequate green spaces, urban engineering has the potential to significantly improve the quality of human life.

Sejong City’s double illusion urban structure

Sejong City has adopted a double annular urban structure instead of grid-like roads like Jujak-daero. In the past, annular cities were designed to reduce the number of intersections and prevent environmental damage by placing circular roads on the outskirts of the city. It also increased the sense of unity among residents, which compensated for the alienation that occurs on grid-like roads. Sejong City went further than this by introducing a double-ring urban structure. This structure divides the city into two rings, with the inner ring consisting of greenery and parkland to provide a place for citizens to relax, and the outer ring containing residential, administrative, and commercial areas centred around the public transport axis to efficiently distribute urban functions.
This dual-illusory urban structure enables efficient land use while protecting the environment, and contributes to enhancing the unity of the urban community by activating communication between residents. Sejong City has become a model for balancing urban functions while effectively managing urban sprawl.

Smart cities and the future of urban engineering

Urban engineering is not just about solving current problems, it also plays an important role in shaping the cities of the future. Today’s cities are evolving beyond the traditional concept of planned cities to become smart cities. Smart cities use information and communication technology (ICT) to optimise traffic, energy, and environmental management to improve the efficiency of city operations. Sejong City has also adopted this concept, utilising advanced technologies such as automation of the transportation system, energy efficiency, and real-time environmental monitoring.
Smart cities aim to provide a better citizen experience by maximising the connectivity of infrastructure within the city. For example, they are optimising public transport systems and considering the introduction of autonomous vehicles to establish their role as cities of the future. These technologies are not just about making life easier, they are also about environmental sustainability and making cities more competitive.
As you can see, urban engineering plays an important role in every aspect of our lives, even if we don’t always notice it. Urban engineering is a multidisciplinary field that combines social sciences, engineering, art, and philosophy, and is a key contributor to the planning and development of cities. In particular, it is becoming increasingly important as cities like Sejong City present new forms of life and prepare for the future through innovative urban structures.