Kanko Mie, the prefectural tourism association, puts the colour at Kaochidani in the second half of November — mid-month to late, a fortnight later than most of the gorges further north.

The valley follows the Shorenji river, a tributary of the Nabari, and its walls are columnar jointing: rock that has cooled and cracked vertically, so that the cliffs read as bundles of standing columns rather than as layers. The local description is that the hillside looks split with an axe. It runs for about eight kilometres, and two formations along it have names — Tengu-bashira-iwa, the goblin's pillar, and Byobu-iwa, the folding screen. The names are literal. One is a column and one is a wall.

That geology is why this gorge is worth a specific trip rather than a general one. The rock is grey and hard-edged, and the maples grow in whatever the columns will hold, so the red arrives in patches against stone instead of filling the whole view. It is a valley to look at for shape as much as for colour.

A road runs the length of it beside the water. Driving through takes very little time and shows you the least; walking any part of it gives you the height of the walls, which is the thing photographs consistently fail to carry. Nabari is the nearest town, and the approach is straightforward from either the Osaka or the Nagoya side.