In November, four thousand maples change color in the hills of Mikawa.

Korankei is a gorge cut by the Tomoe River as it runs toward the Yahagi, curling around the foot of Mount Iimori—a stretch of roughly one kilometer between two bridges. It is not large. That is part of its character: the color is concentrated rather than scattered.

The beginning has a date. In 1634, the eleventh abbot of Kojakuji Temple, a monk named San'ei, planted maples and cedars along the four or five hundred meters of the approach to his temple, reciting the Heart Sutra as he set each one in the ground. Two of the cedars he is said to have planted are still standing. Three centuries later, townspeople took up the work, planting again along both banks, and in 1930 the valley was given the name it carries now.

Because eleven species of maple grow here, they do not turn together. Scarlet stands beside vermilion beside orange beside a branch still stubbornly green, so that on any given day in late November you are looking at four different autumns at once.

The classic view is from Taigetsukyo, the red bridge over the river; from its middle the water below runs red, the bridge's own vermilion doubled in the current. Walk from the bridge to the temple and the mountain gate frames the maples like a picture. From behind the temple a path climbs to the summit of Iimori in about twenty minutes.

During the festival the trees are lit from sunset until nine. Nagoya is an hour by car, and on an autumn weekend the lots fill early enough that arriving with the morning is the only comfortable plan.

What stays with you is the arithmetic. One monk, one seedling at a time, and three hundred years before the valley finished turning red. He never saw it. He planted anyway.