From the air, it looks like an ink spill in turquoise water, a perfect circle that seems to drop straight into the planet. For decades, Belize’s Great Blue Hole has pulled in explorers, filmmakers and ...

Deep in the Arctic Circle, there’s a man-made hole that once earned the nickname “the entrance to hell.” The Kola Superdeep Borehole, the deepest hole ever drilled on Earth, reached a staggering 12 ...