Travelling from K2 in Pakistan to Ladakh in India. It is a short distance as the crow flies but, due to politics, a huge loop. He passes through the Sikh city of Amritsar, with its Golden Temple, and through Shimla with its Vice Regal Lodge, Gaiety Theatre and cosy half-timbered tea-houses. He then meets the 14th Dalai Lama in Dharamsala, where the Tibetan government is in exile.

In the last episode, Iain discovers the remarkable impact of just one plant: grass. On the savannah of South Africa he sees how grass unleashed a firestorm to fight its greatest enemy, the forests. He shows how cutting your finger on a blade of grass shows us how it transformed life in the oceans. In Senegal, he meets the cleverest chimps in the world. And, in the ruins of the oldest temple on Earth, he tells the extraordinary story of how grass triggered human civilisation.

Particle physicist Prof. Brian Cox asks, 'What time is it?' It's a simple question and it sounds like it has a simple answer. But do we really know what it is that we're asking? Brian visits the ancient Mayan pyramids in Mexico where the Maya built temples to time. He finds out that a day is never 24 hours and meets Earth's very own Director of Time. He journeys to the beginning of time, and goes beyond within the realms of string theory, and explores the very limit of time. He discovers that we not only travel through time at the speed of light, but the experience we feel as the passing of time could be an illusion.

The magnificent ancient city of pyramids at Caral in Peru is a thousand years older than the earliest known civilisation in the Americas and, at 2,627 BC, is as old as the pyramids of Egypt. Many now believe it is the fabled missing link of archaeology - a 'mother city'. If so, then these extraordinary findings could finally answer one of the great questions of archaeology: why did humans become civilised?" For over a century, archaeologists have been searching for what they call a mother city. Civilisation began in only six areas of the world: Egypt, Mesopotamia, India, China, Peru and Central America. In each of these regions people moved from small family units to build cities of thousands of people. They crossed the historic divide, one of the great moments in human history. Why? To find the answer archaeologists needed to find a mother city - the first stage of city-building. Caral, is so much older than anything else in South America that it is a clear candidate to be the mother city. It also is in pristine condition. Nothing has been built on it at all. Instead laid out before the world is an elaborate complex of pyramids, temples, an amphitheatre and ordinary houses. Scientists developed a number of theories. Some said it was because of the development of trade, others that it was irrigation. Some even today believe it was all because of aliens. Gradually an uneasy consensus emerged. The key force common to all civilisations was warfare. Crucially, there is not the faintest trace of warfare at Caral; no battlements, no weapons, no mutilated bodies. Instead, Ruth's findings suggest it was a gentle society, built on commerce and pleasure. In one of the pyramids they uncovered beautiful flutes made from condor and pelican bones. They have also found evidence of a culture that took drugs and perhaps aphrodisiacs. Most stunning of all, they have found the remains of a baby, lovingly wrapped and buried with a precious necklace made of stone beads.

Stonehenge was shaped over centuries, but to what purpose? Was it a temple to the sun, or the moon, an astronomical calendar, or a shrine to dead ancestors? Now Stonehenge may be about to give up some of its secrets. For the first time in nearly half a century a new archaeological dig the sacred stone circle. And the men who are leading the excavation are well aware of the significance of this moment.
The film exposes an investigation into a radical theory that Stonehenge, far from being a place of burial as is commonly assumed, was in fact a place of healing. The investigation takes in forensic testing of bones excavated over the past decades and hard-won permission for the first dig in 50 years at the Henge, watched live online by millions of viewers around the world. Does the theory of the healing stones bear up to modern-day forensic science?

The architectural design of Beijing's ancient complex of palaces and temples enabled it to survive centuries of earthquakes. The Forbidden City is the world’s biggest and most extravagant palace complex ever built. For five centuries, it was the power center of imperial China and survived wars, revolution, fires, and earthquakes. How did the Ming Emperor’s workforce construct its sprawling array of nearly 1,000 buildings and dozens of temples in a little over a decade?