What are some factors that would promote the gtowth of a town into a large city?

Some of the factors are:
-Moderate climate. 
-central geography,
-ease of transportation,
 -highways,
-railroads,
-location near a large body of water

Large cities tend to develop far from cities that had either too hot or too cold temperature. It also must be easily accessible by other regions and provide the people with necessary resources that help them sustain their living (such as water, food crops, woods, etc)