Millions live there, millions more visit each year - but how many really know London?
Find out:
* How New York's famous Central Park came to be modelled on a seventeenth-century London square
* When Primrose Hill almost gained a pyramid even larger than the Great Pyramid of Cheops
* Why about 640 people came to be drowned in the Thames in a single night
* What the royal family might do to escape London if the balloon ever goes up