This episode tells the story of how the Emperor Constantine brought Christianity to the western world. In AD 312, Rome was in crisis. The empire had been divided into four parts, each with its own emperor who fought one another. Constantine intervened and united Rome, using military might and a new religion - Christianity.

In AD 410, the Goth hordes sacked the city. This event symbolised Rome's collapse. Within 70 years, the western empire - what we think of as Ancient Rome - was abandoned. But it should never have happened at all.

In part 2, we take a look at Odysseus, whom Homer made famous in "The Odyssey," including his adventures in light of astronomical and geographical evidence which bases the story on accurate real events.

Through the mountains and jungles of Colombia, Cooper goes in search of the truth behind one of the greatest stories ever told - the legend of El Dorado. His journey takes him from Bogota to the Caribbean coast, through territories once dominated by two cultures, the Muisca and the Tairona, who flourished for centuries before the arrival of the Spanish in the 16th century. Cooper reveals forgotten peoples who valued gold in a way the Western world still struggles to understand, travelling to an astonishing lost city and meeting the last survivors of an ancient civilisation.

This four-part British television series outlines aspects of the history of mathematics. Written and presented by University of Oxford professor Marcus du Sautoy, it is a co-production between the Open University and the BBC. In the first episode, Marcus du Sautoy in Egypt uncovers use of a decimal system based on ten fingers of the hand and discovers that the way we tell the time is based on the Babylonian Base 60 number system. In Greece, he looks at the contributions of some of the giants of mathematics including Plato, Archimedes and Pythagoras, who is credited with beginning the transformation of mathematics from a counting tool into the analytical subject of today. A controversial figure, Pythagoras’ teachings were considered suspect and his followers seen as social outcasts and a little be strange and not in the norm. There is a legend going around that one of his followers, Hippasus, was drowned when he announced his discovery of irrational numbers. As well as his work on the properties of right angled triangles, Pythagoras developed another important theory after observing musical instruments. He discovered that the intervals between harmonious musical notes are always in whole number intervals.

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.