The striped hills of Zhangye Danxia, in the dry northwest of China, are the floor of a lake that dried out while dinosaurs were alive — stood on end, then cut open. Sand and silt settled here bed by bed, each with its own chemistry. Where the mud held iron that had rusted in oxygen-rich water it baked brick-red and rust-orange; where the iron never rusted, the same rock came out grey-green, yellow-grey or cream. The collision that raised the Himalaya tipped the whole stack on its side. Erosion then cut across the tilted layers, so the bands run as diagonal ribbons up the ridges instead of lying level. Boardwalks and stairways climb to platforms along the tops. From the railing you can watch the stripes resolve into fine grains of mudstone, one colour giving way to the next with no blur in between.
What the hills look like depends entirely on the hour. If you come at midday, under the flat glare, they wash out pale and dusty. As the sun drops, its light rakes along the ridges. The red bands deepen to ember, the shadows pick out every layer, and the platform facing the sunset fills around you for as long as it lasts. These ridges stand at the edge of the Hexi Corridor, the old Silk Road route between China and the west, with the city of Zhangye a stop along it. Caravans passed the hills for centuries, and it still took a film crew to make the rest of the world look. A dark comedy shot among the slopes in 2009 sent Chinese and then foreign visitors to a landscape most had never heard of. The best version of the place belongs to a storm. When a summer downpour passes over and the sun comes back onto wet rock, the reds and greens saturate far beyond anything a dry evening can give you, and the colour drains away again as fast as the hills dry.