The Rainbow Mountains of Zhangye Danxia — Gansu, China

In the northern foothills of the Qilian Mountains, in Gansu province in northwest China, the hills are striped. Zhangye National Geopark covers 322 square kilometres — about 124 square miles — of ridges banded in rust red, ochre, cream and pale green, laid down as sandstone and other mineral deposits over some 24 million years. Left flat, they would be nothing remarkable. What makes them a landscape is that the whole stack was tilted on edge by the same tectonic movement that raised parts of the Himalayas, so the layers now run diagonally up and across the slopes instead of lying level. Wind and rain then spent a very long time carving the tilted layer cake into towers, pillars and ravines, and every cut exposes the banding again at a new angle.

The colours are real, not a trick of processing. Danxia is a Chinese term for a particular kind of terrain built from red beds — sandstones and conglomerates stained by iron and other minerals — and geologists sometimes call it pseudo-karst, because it looks like limestone country from a distance while being made of something else entirely. Zhangye is the best-known example in the arid northwest. The park became a provisional geopark in April 2012, was formally designated Zhangye National Geopark in June 2016, and joined the UNESCO Global Geopark network in 2019. Worth knowing, because it is a common mix-up: the China Danxia World Heritage listing of 2010 covers six danxia areas in southern China and does not include Zhangye. There are three scenic areas here — Linze, the most developed, is about 30 kilometres west of downtown Zhangye; Binggou opened in August 2014 and covers 300 square kilometres at elevations between 1,500 and 2,500 metres; Sunan lies further south. Boardwalks and access roads thread between the formations so people can walk in without walking on them.

As a jigsaw this one rewards patience with a very unusual sorting rule: ignore colour, follow the stripes. Almost every piece in the lower two-thirds carries at least one band running across it, and because the layers were tilted together they all lean the same way — once you have found that angle, pieces snap into sequence far faster than hue alone would allow. The sky is the easy start, a clean blue gradient with a bank of cumulus on the right giving the top edge some anchors. Then work the ridgeline where the coloured hills meet the sky, because the silhouette is jagged and highly distinctive. Leave the deep red foreground mounds until last; they are the most uniform part of the frame, and the thin pale track curving through the middle distance is the connector that finally joins the near ground to the far.