The final episode of Human Planet looks at the environment which has been made by humans for humans. Cities are our greatest success story and now over half the world's population lives in the urban jungle. They are built to keep untamed nature out, but nature cannot be pushed away. From bed bugs sucking our blood at night, to rats in our restaurants, gangs of monkey muggers and rutting elks in downtown USA, many animals have adapted to living in a world of bricks and steel.