How would you translate 魔都 in English?
You can use Demon City.

魔都 (used for 上海) came from the novel 魔都 written by 村松梢風 in 1924, and according to wikipedia, the novel's name is translated as Demon City.

Note that you don't have to translate 都 into capital, because it means big city too.


  ● 都
  　1. 大都市：～市。～会。通～大邑。