Xinjiang (historic East Turkestan) is the (autonomous) province inhabited for centuries by Muslim Uighurs, which belongs since 1949 to the Chinese People's Republic. Capital of the province is Urumqi, while Kashgar is the historical center.
The pictures come from a trip undertaken by the Institute for Turkology at the Free University of Berlin in autumn 2006, before the Olympic Games in Beijing in 2008 and the increasingly repressive Chinese policy against the Muslim Uighurs, which resulted in the destruction of irreplaceable cultural monuments (e.g. the old town von Kashgar).
For the current political situation and the surpression of the Uighurs see https://www.independent.co.uk/voices/china-uighur-prison-camps-leak-papers-xinjiang-a9217671.html
For the destruction of the Muslim cultural heritage see the article in the Guardian https://www.theguardian.com/world/2020/sep/25/thousands-of-xinjiang-mosques-destroyed-damaged-china-report-finds