The Celts - one of the world's most mysterious ancient people. In Britain and Ireland, we are never far from our Celtic past but in this series Prof. Alice Roberts and archaeologist Neil Oliver travel much further afield, discovering the origins and beliefs of these Iron Age people in artefacts and human remains right across Europe, from Turkey to Portugal. What emerges is not a wild people on the western fringes of Europe, but a highly sophisticated tribal culture that influenced vast areas of the ancient world - and even Rome". Rich with vivid drama reconstruction, we recreate this pivotal time and meet some of our most famous ancient leaders - from Queen Boudicca to Julius Caesar - and relive the battles they fought for the heart and soul of Europe. Alice and Neil discover that these key battles between the Celts and the Romans over the best part of 500 years constituted a fight for two very different forms of civilisation - a fight that came to define the world we live in today. In the first episode, we see the origins of the Celts in the Alps of central Europe and relive the moment of first contact with the Romans in a pitched battle just north of Rome - a battle that the Celts won and that left the imperial city devastated.

Four and a half billion years ago, the young Earth was a hellish place, a seething chaos of meteorite impacts, volcanoes belching noxious gases, and lightning flashing through a thin, torrid atmosphere. Then, in a process that has puzzled scientists for decades, life emerged. But how? Join mineralogist Robert Hazen as he journeys around the globe. From an ancient Moroccan market to the Australian Outback, he advances a startling and counterintuitive idea—that the rocks beneath our feet were not only essential to jump-starting life, but that microbial life helped give birth to hundreds of minerals we know and depend on today. It's a theory of the co-evolution of Earth and life that is reshaping the grand-narrative of our planet’s story.

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

Acclaimed National Geographic photographer James Balog was once a skeptic about climate change. But through his Extreme Ice Survey, he discovers undeniable evidence of our changing planet. In Chasing Ice, Balog deploys revolutionary time-lapse cameras to capture a multi-year record of the world's changing glaciers". His hauntingly beautiful videos compress years into seconds and capture ancient mountains of ice in motion as they disappear at a breathtaking rate. Traveling with a team of young adventurers across the brutal Arctic, Balog risks his career and his well-being in pursuit of the biggest story facing humanity. As the debate polarizes America, and the intensity of natural disasters ramps up globally, Chasing Ice depicts a heroic photojournalist on a mission to deliver fragile hope to our carbon-powered planet. Directed by Jeff Orlowski

More than 2,000 years ago, the thriving city of Petra rose up in the bone-dry desert of what is now Jordan. An oasis of culture and abundance, the city was built by wealthy merchants whose camel caravans transported incense and spices from the Arabian Gulf. They carved spectacular temple-tombs into its soaring cliffs, raised a monumental Great Temple at its heart, and devised an ingenious system that channeled water to vineyards, bathhouses, fountains, and pools. But following a catastrophic earthquake and a slump in its desert trade routes, Petra's unique culture faded and was lost to most of the world for nearly a thousand years. Now, in a daring experiment, an archaeologist and sculptors team up to carve an iconic temple-tomb to find out how the ancient people of Petra built their city of stone. Meanwhile, scientists using remote sensors and hydraulic flumes uncover the vast city and its sophisticated water system. The race is on to discover how these nomads created this oasis of culture in one of the harshest climates on Earth.

Ancient Aliens explores the controversial theory that extraterrestrials have visited Earth for millions of years. From the age of the dinosaurs to ancient Egypt, from early cave drawings to continued mass sightings. In this episode researchers discuss the possibility that the great technological developments made by inventor Nikola Tesla were inspired by extraterrestrials