SONGPAN, 320km north of Chengdu, was founded in Qing times as a garrison town straddling both the Min River and the main road to Gansu. Strategically, it guards the neck of a valley, built up against a stony ridge to the west and surrounded on the remaining three sides by 8m-high stone walls. These have been partially restored, and you can walk between the north and east gates and above the south gate. Though increasingly touristed, Songpan’s shops, stocked with handmade woollen blankets, fur-lined jackets, ornate knives, saddles, stirrups, bridles and all sorts of jewellery, cater to local Tibetans and Qiang, another mountain-dwelling minority. In spring, Songpan – along with every town in western Sichuan – becomes a marketplace for bizarre caterpillar fungus (虫草, chóngcăo); for more on this strange trade.