Brilliant! If you don't quite get it, just keep looking at the cards of one colour and notice: 1. how the individual cards make one colour; 2. how the cards have been shrunk into different sizes to show this. Don't give up on this image until you "get it"! This picture is a work of art, and someone must have spent a great deal of time making it. 10/10.
Nice work whoever made this. My only suggestion would be to remove the black borders, but I see there's already an image like that. This is therefore interesting as it shows how the images on the cards 'zoom' into each Lost City.
Now I understand why they are called "expeditions"! This image beautifully shows how all the card pictures (of one colour) form one picture of one expedition, culminating of course in a lost city. Lovely!
This image here is similar, and equally outstanding:
See also:
These are classic examples of a polyptych, which is a term to describe pictures divided into multiple panels/sections. There's quite a large number of games that feature a polyptych, see a pictorial gallery here:
It is especially prevalent in Magic the Gathering, a game in which the designers have created many many polyptychs and diptychs (two panels) on the lands. For more information and pictorial examples, see this article: