For centuries, the Northwest Passage, the long-sought sea route connecting the Atlantic and Pacific Oceans through northern Canada, was a holy grail of Arctic exploration. Even now, sailing through it isn’t guaranteed. Mark Synnott, a National Geographic Explorer, writer, and adventurer,...

There’s a lost continent waiting to be explored, and it’s right below our feet. We’ll dig into the deep human relationship to the underground—and why we understand it from an instinctive point of view, but not so much from a physical one. (Hint: We’re afraid of the dark.) In an episode originally...