Soo... everyone has a different idea of what makes a BIG city. I guess it is relative to where you live. For example, if you live in Iceland, any city above 3,000 people is a big town.

In the western US, some might say anything above 100,000 is big. In the eastern US it is anything above 500,000.
In India it's anything over 3 million.

So it really depends.