In Bhutan, Palin finds himself back in the land of yaks for a last look at the high Himalaya. Trekking to Chomolhari base camp he meets a nomad with a penchant for yak songs before heading down to Paro to witness the Buddhist festival or Tsechu. In a bar in Thimphu, he discusses reincarnation and the pursuit of happiness with Benji and Khendum, two of the king's cousins, and en route to Bangladesh is taken by Benji to see the rare black-neck cranes. On his journey south through Bangladesh, Michael visits the ship-breaking beaches of Chittagong and grid-locked Dhaka. He meets a man who made a fortune in Birmingham in the poultry business, and a woman who lends money only to women. On a 1920s paddle steamer he is serenaded with the words of Bengal's Shakespeare, and he completes his epic Himalayan journey aboard a fishing boat that carries him out into the Bay of Bengal and a westering sun.

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.

Jerusalem immerses audiences into one of the world's most beloved cities. Discover why this tiny piece of land is sacred to three major religions through the stories of Jewish, Christian and Muslim families who call Jerusalem home. Join renowned archaeologist, Dr. Jodi Magness, as she travels underground to solve some of this city's greatest mysteries. Find out why, after thousands of years, Jerusalem and the Holy Land continue to stir the imagination of billions of people. Unprecedented access to the city's holiest sites, as well as rare and breathtaking aerial footage of the Old City, combine to make Jerusalem a unique and stunning cinematic experience.

In the fourth episode, Professor Marcus du Sautoy concludes his investigation into the history of mathematics with a look at some of the great unsolved problems that confronted mathematicians in the 20th century. After exploring Georg Cantor's work on infinity and Henri Poincare's work on chaos theory, he sees how mathematics was itself thrown into chaos by the discoveries of Kurt Godel and Paul Cohen, before completing his journey by considering some unsolved problems of maths today, including the Riemann Hypothesis.

Professor Simon Schaffer presents the amazing and untold story of automata - extraordinary clockwork machines designed hundreds of years ago to mimic and recreate life. The film brings the past to life in vivid detail as we see how and why these masterpieces were built. Travelling around Europe, Simon uncovers the history of these machines and shows us some of the most spectacular examples, from an entire working automaton city to a small boy who can be programmed to write and even a device that can play chess". All the machines Simon visits show a level of technical sophistication and ambition that still amazes today. As well as the automata, Simon explains in great detail the world in which they were made - the hardship of the workers who built them, their role in global trade and the industrial revolution and the eccentric designers who dreamt them up. Finally, Simon reveals that to us that these long-forgotten marriages of art and engineering are actually the ancestors of many of our most loved modern technologies, from recorded music to the cinema and much of the digital world.

Born in Naples, Bernini was an exceptional talent from an early age and went on to dominate the art world of 17th century Rome. His work epitomised the Baroque style and his sculpture, church interiors and exteriors and town planning could be seen everywhere. Bernini worked under successive Popes; Pope Gregory XV made him a knight and Pope Urban VIII made him as his best friend. He was revered in his time until a jealous rage caused him to have the face of his mistress slashed after discovering her romance with his brother. His reputation fell further after his bell towers for the Cathedral of St Peter's started cracking in 1641. He redeemed himself and kick started his career again with what is arguably his most famous work, The Ecstasy of St Theresa, in 1652.