This is the 4308th most frequent Chinese word.
山区
Mountain area.
Here, "山区" refers to a geographical location characterized by mountains.
山区的天气变化无常，出门时需携带雨具。
The weather in the mountainous area is unpredictable; it's necessary to carry rain gear when going out.
In this sentence, "山区" pertains to an activity location associated with characteristics typical of mountain areas.
在山区徒步可以享受自然的美景和宁静。
Hiking in the mountainous area allows one to enjoy natural beauty and tranquility.
"山区" in this instance highlights remote or inaccessible regions that require infrastructure development.