How hard could learning a map of a city be? In London, earning the credentials to drive one of the city’s iconic cabs is equivalent to earning a university degree. It’s so advanced, in fact, that being able to navigate the streets isn’t just considered knowledge, but is formally called “The Knowledge.” The way London’s taxi drivers talk about it, it seems a little like getting a black belt in karate while becoming an Eagle Scout while vying for admission to Mensa.

The reason why is London’s curious urban design, a squirrely mix of streets that were designed over centuries rather than by a one-time urban design grid that you might find in New York or Washington