"How boring would the world be," asks Simon Garfield, "if we knew precisely where everything was?" Simon reflects on the many mistakes and deceptions in some of our best-loved maps. He begins with the map of the London Underground where lines on the map bears little resemblance to reality but is "informationally brilliant". He talks about California, the subject of a "sustained cartographic foul-up": for 200 years it appeared on maps as an island, and it continued to do so even after navigators had tried to sail all the way round it - and failed. And then there's "one of the great phantoms in the history of cartography" - the Mountains of Kong. They were apparently a wide central mountain belt that in the eighteenth-century appeared to stretch across thousands of miles of West Africa. Despite being repeated on map after map for almost a century, however, they were a pure figment of imagination. Simon celebrates these mistakes, describing them as the "accidental discovery...of searching souls". In these days of digital maps, he hopes that we can still find "strange and charming and wonderful things - mountains that don't exist and islands of the imagination". Producer: Adele Armstrong.