Mini Metros shrinks and simplifies 220 subway and light rail systems; the end result fits on a single sheet. Its creator, Peter Dovak, explains the challenge of making small and simple representations of sometimes inordinately complex transit systems:

All of the cities in the project had the same requirements: they had to fit in a 120px circle (with 10px of padding), the lines had to be 3px wide with a minimum of another 3px between the next parallel line, and all diagonals had to be 45-degrees. The systems themselves needed to be full-fledged heavy rail metro systems or light rail networks that were distinct enough from trolleys or streetcars.

Prints and mugs are available. [Maptitude]