How is the street pattern inside Seoul’s old city different from the streets outside the central basin?

The street pattern of Seoul varies significantly between the historic central basin and the areas beyond it:

• Inside the Old City: The central district, located within the sites of the four major gates, is characterized by a rectangular grid pattern. While topographic irregularities near the surrounding hills influence some streets, the primary layout remains oriented in a grid, with major thoroughfares such as Jongno and Euljiro running east to west.1
• Outside the Central Basin: In contrast to the grid-based center, the street pattern outside the basin area features a number of radiating streets that are interconnected by a series of concentric circular roads.1

This distinction reflects the city's historical development, as the original district was planned as the capital of the Joseon dynasty in 1394, while the expansion into the surrounding areas occurred much later, particularly during the rapid urbanization of the 20th century.12