Iain visits an extraordinary crystal cave in Mexico, drops down a hole in the Iranian desert and crawls through seven-thousand-year-old tunnels in Israel. His exploration reveals that throughout history, our ancestors were strangely drawn to fault lines, areas which connect the surface with the deep interior of the planet. These fault lines gave access to important resources, but also brought with them great danger.

Visiting spectacular locations in Iceland, the Middle East and India, Professor Ian Stewart shows how control over water has been central to human existence; in the Himalayas, villagers have built a living bridge to cope with the monsoon.

Professor Iain Stewart explores out turbulent relationship with the wind.

Fire has long been a source of energy; how it played a crucial role in Britain's industrial revolution, while holding China's development back.