If you live in a city, the river is more than a landmark, more than something to help get one's bearings or a line to cross - it defines the space.
One's geographical, cultural and even social compass is guided by the slow and steady sweep of a river's path through a conurbation.
To the ancient Pharaohs of Egypt, the East Bank of the Nile was the side of life, the West, where the sun set, the side marked out for death and the journey to the afterlife.
In Paris, the Rive Droite is associated with elegance and sophistication, unlike the dangerously bohemian Rive Gauche.
In London? Well, ask any taxi driver and they'll explain how the capital is really two separate cities - "norf" and "sarf", a division which no number of bridges and tunnels can ever unify.
So the idea that graphic simplicity should dictate the river be removed from the iconic tube map of London is controversial to say the least.
continued at: Map of the Week