Hop in a taxi and your experience will typically feature the following: a chatty driver with opinions on almost everything, a route that takes what feels like a hundred turns, and no dashboard GPS device to guide the cabbie through the city's labyrinthine streets.
For all that, you can thank the Knowledge, a 153-year-old system for memorizing every street and landmark in a six-mile area of central London. The Knowledge requires all cabbies to navigate between any two points in the city entirely from memory. Hopeful drivers study for three to fours years, traverse London on a motor scooter to learn the shortest routes across town and are required to pass a series of intense oral exams -- all before they can get behind the wheel of a taxi. It's a process unmatched anywhere in the world.
Before you can drive one of these, you have to learn every street in London.
