Start: Bukhansan National Park (directions below)
Difficulty: Varies. Mostly Moderate/Difficult
Bukhansan National Park boasts a huge array or trails. I have always taken the Subway to Gupabal Station and then bus 704 to the mountain, but you can also start on the opposite side at Gireum Station. This is one of the most popular places to hike around Seoul, so go early or be prepared to spend your day walking in a line.
Most of the runs are extremely challenging and steep. Almost every trail leads to a summit, some require handrails to climb, and some require scrambling up rocks. Overall, the runs are not mellow enough to really hit a groove, but they can definitely push you hard. Also be warned that the trails can be very rocky in places, so make sure you have good trail running shoes before heading here. If you pack a lunch and a CamelBack, it can be a good all day hiking/running adventure due to the size of the park, and the views from the summits are amazing.
I won’t shoot for any specific route description. Grab a foldable map (though they’re not very well detailed) at the visitors’ center as you enter the park, and pick your poison. Each trail offers something new, but as I warned earlier is better here.