Nakatsu gorge is known for the colour of its water, which is a strange thing to lead with in autumn, and exactly the right one. The viewing time here is mid-November. What you come for is the combination: maple red hanging over water that reads distinctly blue.

The gorge climbs about five hundred metres up from national route 33, a prefectural natural park cut by rain falling on Mount Nakatsumyojin over spans of time that make the walk feel brief. A path runs roughly two and a third kilometres from the entrance to a standing stone at the far end. Partway along, Uryu Falls appears head-on from a viewing platform; a hundred metres of climbing beyond that is Ryugubuchi, the pool where the blue shows clearest. Red above, blue below — opposite ends of the spectrum in one frame, arranged by nobody.

One of the falls along the route is called Momiji. The place named itself for this season a long time ago, and it has been keeping the appointment ever since.

At the mouth of the gorge stands a hot spring inn that takes day visitors. The stone stays wet beside the pools, so give the descent more care than the climb. Then the correct ending, in the correct order: walk the gorge, see the blue, get in the bath. You will be warm again before you reach the road.