Northern Central Region of China.
This is one of the areas where Chinese civilisation first developed, along the Yellow River.
As anywhere in China, Mandarin is the lingua franca; nearly everyone can speak it. The Mandarin spoken in this region, especially around Beijing, is the standard dialect. Inner Mongolia naturally has many speakers of Mongolian, but many of them speak Mandarin as well. Russian is fairly common as a second language. As elsewhere in China, English is not widespread but some people speak it quite well.