URUMQI, China—In this old Silk Road city in western China, a state security campaign involving the detention of vast numbers of people has moved to its next stage: demolishing their neighborhoods and purging their culture.

Two years after authorities began rounding up Urumqi’s mostly Muslim ethnic Uighur residents, many of the anchors of Uighur life and identity are being uprooted. Empty mosques remain, while the shantytown homes that surrounded them have been replaced by glass towers and retail strips like many found across China.

Food stalls that sold fresh nang, the circular flatbread that is to Uighur society what baguettes are to the French, are gone. The young men that once baked the nang (or nan in Uighur) have disappeared, as have many of their customers. Uighur-language books are missing from store shelves in a city, the capital of China’s Xinjiang region, that has long been a center of the global Uighur community.

Supplanting the Turkic culture that long defined large parts of Urumqi is a sanitized version catering to Chinese tourists. On a recent morning in the Erdaoqiao neighborhood, the once-bustling heart of Uighur Urumqi, nang ovens were nowhere to be seen—but souvenir shops sold nang-shaped pocket mirrors, nang bottle openers and circular throw pillows with covers printed to look like nang.