Constructed in 1396 to protect the capital from invasion, Hanyangdoseong is an 18.63 km-long (11.58 mile-long) fortress wall punctuated with eight gates that took 197,400 people 98 days to complete. Although many sections of the colossal wall have been lost to time, about 70 percent of the wall and six of the gates remain intact today. The wall was built in harmony with the city’s natural topography by lining the ridges of Seoul’s four main mountains, making the trails following the wall today a great way to explore Seoul from the ground up. Two sections of the wall lie in the Dongdaemun area and extend north and south from Heunginjimun Gate.
The northern Naksan Mountain Trail follows the remnants of the wall for 2.1 km (1.3 miles) over Naksan Mountain to Hyehwamun Gate, and the southern Heunginjimun Gate Trail extends 1.8 km (1.1 miles) past Dongdaemun History & Culture Park and Dongdaemun Design Plaza to Gwanghuimun Gate. Whichever trail you take, a good place to start is with a visit to the Seoul City Wall Museum set in Dongdaemun City Wall Park.