I recently learned about Eratosthenes who not only was able to figure out the earth was a sphere, but he also accurately measured the earth's circumference.

With an understanding that the earth was over 40,000km, what did they believe was outside the known Greek world?

Did they assume there were other people? Did they believe in the outside world the same way we look at the planets in far-off solar systems—that there must be life but we just don't know about it?

Or did they think that they and the other communities that they were aware of were it?