Incredible But True Incredible But True Human World History Makers Cities Of The World Art And Music Sporting Headlines Plant Life Fish, Amphibians, Reptiles Birds and Mammals Creepy Crawlies Marine Life Restless Earth Earth's Secrets Changing Weather Seas And Oceans Comparisons Amazing Structures Machines And Man World Of Inventions Travelling Around Mysterious Universe	First in Line - Jericho Jericho, in Jordan, is the oldest walled city in the world. It had a population of 2,700 by 7800 BC.   Previous: Back Book: Incredible But True Section: Incredible But True Chapter: Cities Of The World