Given the task definition and input, reply with output. This task is about creating an unanswerable question based on a given passage. Construct a question that looks relevant to the given context but is unanswerable. Following are a few suggestions about how to create unanswerable questions:
(i) create questions which require satisfying a constraint that is not mentioned in the passage
(ii) create questions which require information beyond what is provided in the passage in order to answer
(iii) replace an existing entity, number, date mentioned in the passage with other entity, number, date and use it in the question
(iv) create a question which is answerable from the passage and then replace one or two words by their antonyms or insert/remove negation words to make it unanswerable.

Passage: By the 1st century, Babylonia, to which Jews migrated to after the Babylonian conquest as well as after the Bar Kokhba revolt in 135 CE, already held a speedily growing population of an estimated 1,000,000 Jews, which increased to an estimated 2 million between the years 200 CE 500 CE, both by natural growth and by immigration of more Jews from the Land of Israel, making up about 1/6 of the world Jewish population at that era. At times conversion has accounted for a part of Jewish population growth. Some have claimed that in the 1st century of the Christian era, for example, the population more than doubled, from four to 810 million within the confines of the Roman Empire, in good part as a result of a wave of conversion.
Where did the Jews migrate to before the Babylonian conquest?