Seoul is a city of ten million, and a fortress sits just above its south-eastern edge. Namhansanseong is what the ride calls Area 1, and it is where the Joseon kings used to run when invaders arrived. The wall, about twelve kilometres of stone and earth following the ridge line, was built in the early seventeenth century on the foundations of older fortifications, and the whole enclosure sits on Mount Namhan, a granite hill just beyond Seongnam. It was listed by UNESCO in 2014.
Its story is a bitter one. In the winter of 1636, the Qing army invaded Korea and King Injo fled here with thousands of soldiers and officials. The siege lasted about forty-five days in appalling cold, with food running out, and in January 1637 the king gave up. He walked down to a ford on the Han river called Samjeondo and bowed to the Manchu emperor, an act of submission that Koreans still remember as one of the most humiliating moments in their history. Standing on the wall you can see why it was such a good refuge and why it failed, as the ridge is lovely and the supplies were not.
The area today is a provincial park, wooded and well kept. Roads climb from the plain to the gate, with hairpins and tight bends. At weekends it fills with hikers, cyclists and families, and the car parks, restaurants and chicken-porridge houses are packed. For fuel, Seongnam is one of Korea's bigger cities, with a million people and a station at every junction, so you will not be stuck.
A practical note: motorcycles are barred from Korean expressways, so you will use the national roads, which can be busy but are well surfaced. Speed cameras are everywhere. In this region, an early start on a weekday is the way to find a quiet road.
Spring brings cherry blossoms along the lower road and autumn colours are spectacular on the wooded ridges. Winter is cold and the air is clear, with views over Seoul on good days. Walk a section of the wall if you can; the stones are warm in the afternoon sun.