Just beyond the south-eastern edge of Seoul, the city stops abruptly against wooded mountains, and on top of them runs a stone wall with gates, watchtowers and command posts. Namhansanseong was built as an emergency capital, a mountain fortress where the king and court could retreat in time of invasion, and in the winter of 1636 to 1637 it was put to the test. King Injo fled here from the invading Qing army and held out for forty-seven days before hunger and the fall of other strongholds forced him to surrender. The fortress became a World Heritage Site in 2014.
Today the wall is a popular hiking circuit, and the little settlement inside, with its temples, restored royal residence and command posts, is full of restaurants specialising in slow-cooked chicken and duck. On weekends thousands of Seoulites come up, so weekdays are calmer. In autumn the maples and oaks turn the ridges red and gold, and on clear winter days you can see across the whole city to the mountains north of the Han river.
Before you plan anything else, know this: motorcycles are not allowed on South Korea's expressways. Everything has to be done on national and local roads, which in a crowded urban area means traffic lights, delivery scooters and buses. The reward is the climb to the fortress itself, a twisty road through forest that local riders love, with tight hairpins and good surfaces. Weekend crowds of cars and hikers mean you should keep your speed sensible, especially near the gates and car parks.
Seongnam and Hanam, the big cities at the foot of the mountain, have plenty of fuel, motorcycle shops and food. Gwangju to the south-east, not to be confused with the southern city of the same name, gives access to quieter roads along the Han river and towards Paldang Lake.
Korean summers are hot and very humid, with the monsoon rains of late June and July, and typhoons can bring heavy storms in late summer. Spring, with cherry and azalea blossom, and autumn are the best riding seasons. A bowl of chicken soup inside the fortress, with the noise of the city replaced by birdsong and temple bells, is a good reward for the ride.