Sejong Si (Sejong City), the second capital city of South Korea, is a new city initiated to achieve the national policy agenda of balanced territorial development by mitigating the excessive concentration of public and private facilities in the Seoul metropolitan area (SMA). The master plan for Sejong City was formulated in 2005 through a project initiated by the Korean government and is noteworthy in that it presents a new urban design paradigm of construction reflecting the Korean experience. This paper explores the characteristics of Sejong City’s urban structure and neighborhood design. One major characteristic is Sejong City’s ring-shaped design (decentralized and empty in the central area), which makes the city structurally distinct from other modern cities with hierarchical and symbolic structures. Another major characteristic is the presence of approximately 20 neighborhood units located in accordance with the ring-shaped structure. This is consistent with the transit-oriented development (TOD) and traditional neighborhood development (TND) systems. The urban design method based on TOD and TND models has been effective in terms of Sejong City’s decentralized urban structure. These results are expected to provide a better understanding of urban design for future development projects.