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.

Human civilisation has progressed by learning to deal with the lack and excess of water.

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.

Professor Iain Stewart explores the negative and positive effects that human beings have on the planet's geological cycles.