The Gansu/Xinjiang border is the edge of the world.
Figuratively, of course. But when you’re there it feels plausible. Like when the sand and soil ends, the world ends too. Walk off and you’ll likely fall into infinity.
Although, the friendly owners of Dunhuang’s local guesthouse seem unfazed by the fact that they live so close to boundless space. They have kids and a dog and offered us dried red dates and coal-furnace hospitality in the middle of winter.