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as Oxford University's Janina Ramirez discovers, these sagas are not just great works of art, they are also priceless historical documents which bring to life the Viking world.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.

Bitcoin is the world's leading virtual currency, but unlike real money, it is not backed by a government or properly regulated. Bitcoin is exchanged and held digitally by users - which is attractive to criminals selling drugs, pornography and arms. But now Bitcoin is moving into the mainstream and being openly marketed as an investment opportunity. The film investigates what Bitcoin is and what it means, going inside a Bitcoin mine in Iceland - where currency is made - and spending time with the Bitcoin millionaires of Silicon Valley.
The programme also hears from others who have been scammed out of their life savings and investors who think the cryptocurrency is an enormous scam and that the writing is on the wall. Around the world, authorities are sounding the alarm that Bitcoin is too risky - is it too late, or too crazy, to try to become a Bitcoin millionaire?

Will Smith confronts his fear of nature on powerful white-water rapids in Iceland. "Over five expeditions, I've followed explorers into situations that were straight-up scary. It was worth it to discover the Earth's wonders. But your boy was tripping more than once. Because when I see wilderness, you know, nothing but nature, I get nervous because I don't understand it."