Gareth Leah is a big-wall climber who travels the world looking for the toughest, most remote climbs he can find. A search for 'supervillain lairs' leads him on an odyssey to São Tomé and Principe, Africa to climb the towering Pico Cão Grandé.

Liu Jia is a veteran caver with 12 years’ experience who has made it her mission to explore China's extensive trove of caves. She and her team are drawn to the deepest of them, the Wan Zhang Cave, and set out to explore 1,000m below the surface.

Adrian Mattern is a 20-year-old kayaker with a love for dropping in on waterfalls. He travels from Germany to Hood River, Oregon to hone his skills on some of America's best water, but an unexpected turn shows progression has serious risks.

Russian bouldering champion Vadim Timonov travels to the icy expanse of Lake Baikal, Russia to climb the rocks protruding from the frozen surface. The surreal landscape make this a trip as visually stunning as it is physically challenging.