a circular dot on a map could mean a variety of things. Most likely the dot would indicate a city. Check the legend of your map to find out.
A black dot on a map usually means a city.
a location
The dot or star is your player.
a city
In almost all map systems, a black dot is a city. The larger a dot is, the bigger a city is if there is more than one size on your map.
* = a city
an island or isle
capital city
cities
capitol
capital city