I'm making a big map of the public transport in Brussels. I want to repeat the same circle for all the subway station. So, is it possible to make a clone of this circle. I want to modify all in the same time.
If I copy/paste, I have to change it individually. I don't want it.
You want symbols.
The basic instructions are to drag your artwork for the subway station to the symbols palette, and then drag it out of the palette or copy/paste it for all additional instances of the symbol. To edit all instances, just double-click the symbol.
For more info, see Adobe's page on symbols.