Imagine a world without GPS or sat navs, one where you’d have to commit to memory thousands of streets and landmarks just to get around town. For London’s black cab drivers, that’s all a part of the job. In order to get behind the wheel, drivers must pass The Knowledge, universally regarded as the world’s toughest taxi test. Applicants often take two to four years to prepare for the infamous exam, memorizing over 25,000 street names and 20,000 points of interest. Only one in five applicants pass the test, giving The Knowledge the same success rate as the U.S. Navy SEALs.