One problem with this is that we really do not know what life was like outside of Mohenjo-Daro so we don't know what in the city was better than it was outside the city. So we will simply have to assume that people in other places did not have things that were as good as they were in Mohenjo-Daro.
So, you would want to emphasize the things that were good about the city. One of the things that seems really impressive to us today is the sanitation. You could emphasize how that sanitation leads to better public health. For example "Mohenjo-Daro, where a bath a day keeps the fever demons away." (They probably didn't know that germs cause illness, but they might have noticed that fewer people got sick when they bathed.
Or you could emphasize the fact that nothing in Mohenjo-Daro has been identified as a palace. This implies that they did not have a single king who had most of the wealth. So you could say "Every man a king in Mohenjo-Daro" or "Come to Mohenjo-Daro, where every man is a king."