The original map was designed by Harry Beck in 1931. As you can see in the picture above, which shows the current state of the system, it is very structured and schematic. Displaying only round circles representing stations and straight lines connecting them (which only run horizontally, vertically and at 45 degrees) the map is an abstraction of the actual underground course which is displayed here:
Aside from its instant recognisability due to the unique yet simple design, what makes this concept so great was Beck's realisation that only the topology of the railway mattered, since the physical locations of the stations were largely irrelevant because it was underground and the traveller was only interested in how to get from one station to the other.
