The New York Times Magazine has a fantastic article by Jody Rosen about The Knowledge, which is as much about London taxi drivers as it is about what it is to commit to be the best in a certain field:

The examination to become a London cabby is possibly the most difficult test in the world — demanding years of study to memorize the labyrinthine city’s 25,000 streets and any business or landmark on them. As GPS and Uber imperil this tradition, is there an argument for learning as an end in itself?

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[Matt] McCabe had spent the last three years of his life thinking about London’s roads and landmarks, and how to navigate between them. In the process, he had logged more than 50,000 miles on motorbike and on foot, the equivalent of two circumnavigations of the Earth, nearly all within inner London’s dozen boroughs and the City of London financial district. He was studying to be a London taxi driver, devoting himself full-time to the challenge that would earn him a cabby’s “green badge” and put him behind the wheel of one of the city’s famous boxy black taxis.