metropolis       
noun [ C ]  formal uk/məˈtrɒp.əl.ɪs/ us/məˈtrɑː.pəl.ɪs/
 大城市,大都会;首府;首都
a very large city, often the most important city in a large area or country
  Soon afterwards he left to begin his career in the metropolis. 不久之后他就离开到大城市去开展事业了。 
 a sprawling/bustling/modern metropolis 不断向外扩展的/繁忙的/现代化的大都市