It happened to the Romans, the Anasazi, and the Mayans and, inevitably, one day our own modern civilisation will also fall. In this two hour special discover how a future civilisation might be baffled as to why the population of these once-great cities would suddenly abandon their technology and architecture, and turn their homes into ghost towns. Some experts believe that there is a very real risk this could happen, and the collapse of the world as we know it is closer than we think.