Horses. Powerful, graceful, and thunderously fast. No animal has made a greater impact on society or given humans more freedom and mobility. In a spectacular adventure, the film unlocks the mystery of the first horse warriors on the vast, grassy plains of Kazakhstan, where horses still roam free, and nomadic herders follow their traditional way of life.
Investigating clues from archaeology and genetics, researchers reveal vivid evidence of the very first horsemen. They also discover warriors who swept across Europe and turn out to be the ancestors of millions today.

The last episode examines the fragile interdependence that exists between forests' wide variety of residents, including bald eagles, hunting dogs and Siberian tigers.
Over half of all the world's trees, evergreen and deciduous, stand in great assemblies. For many of us, they are places of mystery and darkness. They are key to our climate, and home to countless unique species. The boreal forest contains 750 billion trees, and it stores over 40 percent of the world's carbon, making it a vital element in the fight against climate change. In the past, we have destroyed them without hesitation. Yet, forests do have an astonishing ability to recover. If we choose to give forests time and space, they could reclothe the earth with much of the rich and varied communities of animals and plants of which we have, so recently, robbed it. A future with more forests is key to the resilience of our planet.

The Vision After the Sermon, also known as Jacob Wrestling with the Angel, is a painting full of symbolism and mystery. But what does Gauguin’s famous work have to do with a 17-year-old girl called Madeleine, with Victor Hugo’s Les Miserables, and with sumo wrestlers?
Waldemar Januszczak reveals all as he investigates Gauguin’s epic religious painting about good and evil, temptation and desire.

A young mother's mysterious death and her son's subsequent kidnapping blow open a decades-long mystery about the woman's true identity and the murderous federal fugitive at the center of it all.
It's late at night in Oklahoma City, in April of 1990. Two or three guys are in a truck driving along the road and they see some kind of debris. And then they see off to the side, there's a body. It appears to be a young woman, a blonde-haired woman and they call an ambulance. She's rushed to the hospital, and her husband, Clarence, eventually shows up. He says her name is Tonya Hughes, that she's a stripper in Tulsa, and that they have a young son named Michael. And he's much older and he's just kind of this weird guy. So, the doctors, as they continue to examine her, they see old bruises and old injuries. There's something wrong with this picture. Ultimately, she passes away. The girls Tonya danced with want to find her family. So they call this woman and they tell her that her daughter died. And she says, 'What are you talking about? My daughter died 20 years ago, she was only 18 months old.' They realize that who they just buried was not Tonya Hughes, so now they're asking, 'What happened?'.

The dome that crowns Florence's great cathedral of Santa Maria del Fiore, the Duomo, is a masterpiece of Renaissance ingenuity and an enduring source of mystery. Still the largest masonry dome on earth, it is taller than the Statue of Liberty and weighs as much as an average cruise ship. Historians and engineers have long debated how its architect, Filippo Brunelleschi, kept the dome perfectly aligned and symmetrical as the sides rose and converged toward the center." More than four million bricks could collapse at any moment -- and we still don't understand how Brunelleschi prevented it. To test the latest theories, a team of U.S. bricklayers will help build an experimental "mini-Duomo" using period tools and techniques.

Whether serving as Christian church, Islamic mosque, or secular museum, Hagia Sophia and its soaring dome have inspired reverence and awe. For 800 years, it was the largest enclosed building in the world—the Statue of Liberty can fit beneath its dome with room to spare. How has it survived its location on one of the world's most active seismic faults, which has inflicted a dozen devastating earthquakes since it was built in 537?" As Istanbul braces for the next big quake, a team of architects and engineers is urgently investigating Hagia Sophia's seismic secrets. Follow engineers as they build a massive 8-ton model of the building's core structure, place it on a motorized shake table, and hit it with a series of simulated quakes, pushing it collapse—a fate that the team is determined to avoid with the real building