Ghosts live here. That's what the Chinese say. They claim this place, a walled fortress abandoned in the 14th century and called Khara Khoto—Black City—is inhabited by demons and spirits.

I understand why. Around me Khara Khoto is a haunting pile of drifted sand that partly covers its 30-foot (9.1-meter) ramparts. Inside the city's walls lie ruins of a once vital kingdom. All that remains is shattered and tawny mud buildings crumbled long ago, scatterings of bleached bones unidentifiable with age, and smashed crockery pots and bowls. Granite millstones—their 3-foot (0.9-meter) faces etched by lines seven centuries old—also sit half-buried in the sand.

In the slanting light of an October sunset the legend of the Black City's violent and bloody end spreads