英语翻译；平谷是一个很小的城市，它位于华北平原北部，燕山脚下，人口只有四十万

平谷不是城市吧？

修改一下
Pinggu is a small town, which is located at the north of North China Plain and the foot of Yan Mountain, only has a population about 400,000.

Pinggu is a small city, which is located in the northern part of North China Plain, at the foot of Yanshan, has a population of only 400,000