When people talk about their hiking goals, around Seoul, the mountains they often name drop are the big ones: Bukhansan (837m), Dobongsan (740m) and Gwanaksan (629m). Featuring on some top 100 lists you'll also find Suraksan (637m) and Buramsan (520m); with their prominent rock faces and intimidating peaks, these two mountains are worthwhile adventures right on the edge of the city.
An especially attractive element of these two lesser peaks is that you can knock them off in a half day.
On Suraksan, the "must-do" route is one that takes in Train Rock. Here, there are fixed ropes that allow you to ascend a steep slab upwards, which leaves you feeling exposed but also quite exhilarated.
On Buramsan, on the west facing side, accessible from Seoul subway, there are three dominant slabs, known as the Yeongshin Rocks. You can climb any one of these if you leave the trail behind. Slabs 2 and 3 are the largest, and can be scrambled without a rope, although you might feel the need for one to inspire you with a little extra confidence. There are few handholds, and no fixed lines, so you rely on the friction of the rock to allow you up.
If either of these mountains interest you, but you'd like the extra security a guide can offer, then don't hesitate to get in touch!