A Korean traditional house, a hanok, is built with a tile roof whose eaves project about a meter beyond the wall line. The tiles are heavy black-grey giwa, the structural assembly underneath is timber, and the projection is calibrated — by tradition, with regional variation — so that the high summer sun, around the solstice, doesn’t reach past the maru, the elevated wooden porch that runs around the inner courtyard. The geometry was designed for the interior, but it has a useful exterior consequence: in Bukchon, where the hanok line up wall-to-wall along narrow stone-paved gilim, the eaves on either side reduce the sun reaching the alley to a thin strip down the middle. At noon in August, in the better-preserved blocks of Gahoe-dong, that strip is fifteen centimeters wide.
The picks below trace the alleys where the eaves are continuous. The premise is midday — Bukchon is most photographed in the morning and the evening, but the geometric shade is sharpest at solar noon, when the eaves are doing their original job. Stay Cool routes you along the alleys where the hanok density is highest (Bukchon-ro 11-gil, Gahoe-ro 31-gil) and away from the wider streets where the eave shadow doesn’t reach across. A practical note: Bukchon is a lived-in neighborhood. Voice down between the houses; respect the signs that ask you not to enter the residential courtyards. The publicly-open hanok — the cultural center, the Bukchon Hanok village house museum — are signposted.
On a colder day or in spring this walk is shorter. The eaves only become really useful as shade above 60° of sun altitude — which in Seoul means roughly mid-May to early August, between 11 and 2. Outside that window the alleys are still pretty; the shade math just isn’t the point.