The Fortress Wall of Seoul refers to the ancient wall and gates that surrounded the city of Seoul, the capital of South Korea. The wall was built in the late 14th century during the Joseon Dynasty, and it served as a defensive fortress to protect the city against foreign invasions. The wall is made of stone, brick, and earth, and it stretches for about 18.6 kilometers in length. The wall is about 6-7 meters tall and varies in thickness from 3-4 meters.

There are eight gates along the fortress wall, each with a unique name and design. The four main gates are the Namdaemun Gate (also known as Sungnyemun), Dongdaemun Gate, Seodaemun Gate, and Hanyangdoseong Gate. The other four gates are known as smaller gates, and they were built to provide additional access points to the city.

In 1963, the South Korean government declared the fortress wall and gates as a national treasure, and in 1997, the wall was designated as a UNESCO World Heritage Site. Today, visitors can walk along the fortress wall and enjoy the views of the city and surrounding mountains. The wall also provides a glimpse into Seoul's history and its significance as a political, cultural, and economic center in South Korea.