On the slopes of Mount Zao, in the deep Tohoku winter, the trees turn into monsters. It happens when supercooled water droplets and windblown snow freeze onto the conifers, layer upon layer, until each tree becomes a grotesque, towering figure of ice. The Japanese call them juhyo — snow monsters — and they cover the mountain in their thousands, a frozen army on the ridgelines.

By day they are white and strange. At night, during the illumination season, they become something else entirely. Colored light is thrown across the frozen forest, and the monsters loom out of the dark in shifting hues, utterly unlike their daylight selves — nightmarish and beautiful at once.

A ropeway carries visitors up to the summit fields, where you pass close among the iced trees, close enough to see the texture of the frost, the whole mountaintop transformed into a gallery of sub-zero sculpture. It is not a gentle place; the cold is serious, the wind that made the monsters still blowing. Dress for it.

The illumination runs on selected nights from late December into late February. What you are seeing is a collaboration no one planned — the mountain and the weather building the forms, the light merely waking them. This phenomenon occurs, in this scale, only on the mountains of northern Japan. To stand among the lit monsters on a freezing night is to see winter itself given a body.