In this programme, Mary descends into the city streets to discover the dirt, crime, sex and slum conditions in the world's first high-rise city. This Rome is not the marble Rome we know, but a vast, messy metropolis with little urban planning, where most Romans lived in high-rise apartment blocks with little space, light, or even sanitation. Forced outdoors into the city streets, she reveals where they went to hang out, get drunk, have sex and get clean. She looks at the Forum as a place of gamblers, dentists and thieves, and she explores the lustiness of Roman bar life and jokes. Finally, exploring law and order from the bottom up, Mary examines how this city really worked. She meets Ancarenus Nothus, an apartment dweller who lived in fear of the rent collector; Notorious Primus, who wrote about his three great pleasures in life - baths, wine and sex; and Unlucky Doris, a seven-year-old girl killed in one of Rome's many fires.

After filming for three years, Planet Earth finally captures the shy Mongolian gazelle. Only a handful of people have witnessed its annual migration. Don't miss the bizarre-looking Tibetan fox, captured on film for the first time. Over six weeks the team follow a pride of 30 lions as they attempt to hunt elephants. Using the latest night vision equipment, the crew film the chaotic battles that ensue at close quarters.

This episode looks at the battle for Moscow and considers why more civilians died in this war than any other in history.

Iain explores man's relationship with fire. He begins by embarking on an extraordinary encounter with this terrifying force of nature - a walk right through the heart of a raging fire. Fire has long been our main source of energy and Iain shows how this meant that the planet played a crucial role in Britain's industrial revolution, whilst holding China's development back. Along the way he dives in a mysterious lake in Oregon, climbs a glacier of salt, crawls through an extraordinary cave in Iran and takes a therapeutic bath in crude oil.

In the last of the series, Julian Richards uncovers new information from the battle in 1066 between Viking warlord Harald Hardrada and King Harold of England that marked the end of the Viking age in Britain. Results from a nationwide genetic survey show where in Britain the Vikings left a measurable contribution.

From stars, galaxies and moons to subatomic particles, black holes and invisible phenomena, discover the most bizarre, mysterious and exotic things in our universe