The city of Kaifeng, with a population of 442 thousand in 1100, fell to the Jurchens (who later called themselves the Jin Dynasty) in 1127. It had a reduced role under non-Chinese rule even though it was a southern capital for the Jin from 1157. Its population inn 1200 was 100 thousand.
Side note: during this period Kaifeng was called Bianjing or Dongjing.
Source for history: Wikipedia article on Kaifeng, accessed March 4, 2017, although some of the material was already known to me from books I've read.