The two fusion cities are divided by a border. In a few diagrams you should define the border.
(00) Make a topographique map with geographical data as a base for your fusion cities area.
(01) How is the border remarkable? What positive space is created to actually build the border? > draw a plan of the masses (extended zoom), are there checkpoints? then make a zoom to each of them. can they be categorised?
(02) What is restricted by the border? What do you need to pass the border? > make a collage.
(03) Who controls the border? (in both directions) > you may work with pictos to cite laws or rules.
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(a) What/who passes the border anyway? > brainstorming
Impulses
You can get inspired by le Monde Diplomatique’s graphical information in English, in French and in German. They have even more local ones, if you need some more detailed information.
Another graphical award winning magazine is Greenpeace Magazin – even maps.
Some videos, too: minor protest, Borders, Dessert Land.