Lhasa, which at 3,700 metres (12,000 feet) above sea level is one of the highest cities on the world, was named by China's Ministry of Environmental Protection last month as one of 10 cities with the country's best air quality.
But today, the picturesque capital of the Tibetan region was enveloped in a thick cloud of pollution that the Hong Kong-based ifeng.Com news website said was caused by dust that had blown in from north of the Tibetan Plateau.
Photos posted online by ifeng.Com showed the world-famous Potala Palace, a sprawling Buddhist complex and UNESCO World Heritage site that previously served as the winter palace of the Dalai Lama, nearly invisible from a few kilometres away.
The images of pollution in the remote tourist destination, as opposed to in the industrial cities of northeast China, took users of the country's popular social networks by surprise.
"Even Lhasa has floating dust," wrote one. "Heaven on Earth is gone."