1. Under favourable conditions, a city with a billion inhabitants could be a very attractive and exciting place to inhabit.
    在顺利的情况下，一个拥有十亿人口的城市会成为令人非常愉快和向往的居住地。

2. If we get those, something like Billion City may someday be built, and it will be a great place to inhabit.
    如果有了这个条件，诸如十亿人口之类的城市总有一天会建成的，并且是非常适于居住的地方。