Prepping is a big deal in the US. There’s even a reality TV show called “Doomsday Preppers”. Prepping is when you stockpile loads of stuff - food, water, medicine - in case of a disaster, nuclear war or an unstoppable virus. Now billionaires are taking it to the next level, building underground mansions and self-sustaining bunkers that look like something out of a zombie apocalypse movie.

Meta CEO Mark Zuckerberg is building a $100 million compound in Hawaii—complete with plans for a huge underground bunker, although he’s described it as a “little shelter, like a basement”. Peter Thiel, the CEO of Paypal tried to build one in New Zealand and Bill Gates, the founder of Microsoft, is rumoured to have underground security areas under every one of his homes.

In this episode BBC reporter Nathalia Jimenez joins us again to chat about what exactly these billionaires are building and what they’re so worried about. And we hear from Lauren, a prepper in the US, about why she thinks it’s important to get organised.

Instagram: @bbcwhatintheworld Email: whatintheworld@bbc.co.uk WhatsApp: +44 330 12 33 22 6 Presenter: Hannah Gelbart Producers: Julia Ross-Roy and Benita Barden Video producer: Baldeep Chahal Editor: Verity Wilde