Rivers provide the essentials of life: fresh food and water. They often provide natural highways and enable us to live in just about every environment on Earth. But rivers can also flood, freeze or disappear altogether!Cities - Surviving the Urban Jungle Human Planet joins Sam Niang, a Laotian fisherman, as he walks a high wire strung above the raging Mekong River rapids on an extraordinary commute to work. There's also a look at the remarkable partnership between Samburu tribesmen and wild elephants in their search for water in the dried-out river beds of Northern Kenya. Plus, a father who must take his two children on a six-day trek down a frozen river - the most dangerous school run on Earth, and the ice dam busters of Ottowa with their dynamite solution to a city centre hold-up.

From the frozen poles to the searing deserts, this episode shows how animals have come up with strategies to survive the uneven amounts of sunlight that fall on our planet over the course of a year. The exception is on the equator, where the duration of day and night remain the same throughout the year. Here, this guaranteed sunlight drives the great diversity of life in the tropical jungles.

Frequent security expos feature companies like Megvii and its facial- recognition technology. They show off cameras with A.I. that can track cars, and identify individuals by face, or just by the way they walk. In China it's been projected that over 600 million cameras will be deployed by 2020. Here, they may be used to discourage jaywalking, but they also serve to remind people that the state is watching. Matching with the most advanced artificial intelligence algorithm, they can actually use this data, real-time data, to pick up a face or pick up a action.
A.I. is a technology that can be used for good and for evil. So, how do governments limit themselves in, on the one hand, using this A.I. technology and the database to maintain a safe environment for its citizens, but not to encroach on a individual's rights and privacies?

Hundreds of years ago in faraway Iceland the Vikings began to write down dozens of stories called sagas - sweeping narratives based on real people and real events. But as Oxford University's Janina Ramirez discovers, these sagas are not just great works of art, they are also priceless historical documents which bring to life the Viking world. Dr Ramirez travels across glaciers and through the lava fields of Iceland to the far north west of the country to find out about one of the most compelling of these stories - the Laxdaela Saga.

The digital possibilities of social control in China have led to an unprecedented level of state surveillance. Through self-censorship or spying on neighbors, surveillance covers not only those perceived as a threat by the government, but increasingly and ever more totally the ordinary citizen: whether buying flowers, taking your child to school, or taking out the trash at night. Big Data and digital technologies are already being used as weapons to curtail freedoms. Step by step, the social and political behavior of the Chinese is changing.
The documentary explores, in intimate detail, digital social control in China by following the experiences of two families and a journalist. Film-maker Jialing Zhang gives an exclusive and previously impossible intimate insight into the interior of China and tells a deeply disturbing story of how the state uses technology to control its citizens as well as propaganda to convince its people to trust it. She tells a deeply disturbing story about technology, (self-) censorship and abuse of power.

Located beneath Russia's Ural Mountains, Orda Cave is legendary among divers for its unique beauty. The cave's waters are clearest in winter, when the land above lies frozen. With temperatures approaching minus 40 degrees, NHK attempts to film the cave for the first time ever using 4K cameras. Scientists give them insight into the cave's origins, enabling the crew to uncover the miraculous story of how the cave was naturally formed 300 million years ago by climate change and a shifting landscape.