China's largest mosque stands in Kashgar, the last great Uyghur stop before the passes into Central Asia, and it is the sand-yellow of the mud-brick houses around it. Its twin-minaret gateway faces the bazaar square; behind lies a courtyard of poplars and water channels where people pray in the shade. Founded in 1442, it anchors an old town still best walked past coppersmiths and bread ovens.