Factorio Forums

Sometimes you dont see enemy bases on the map(When you press the M key)

The map is not magical like in many other games. Either the player or a radar has to be close to the target for the map to be updated. If neither is the case, the map shows the last state of that chunk, without telling if there's a new alien base or not. See this wiki entry to read more about radars.

I know and i dont use radars so i found it my walking close to it

Enemies create new bases.