This transit map of Stuttgart’s rail network, adopted around 2000, was unique: By omitting horizontal and vertical lines and setting all diagonals at 30 degrees, the designers produced the appearance of three dimensions.

“This diagram is the only one of its type in the world,” wrote Mark Ovenden in Transit Maps of the World, “although Harry Beck did experiment briefly with a 60/120-degree variation of the London map in 1940.” Alas, it’s since been superseded.