In the era of Google Maps and GoPros, it's easy to assume that the Earth's most inimitable challenges have all been met: the tallest peaks summited, the most remote rivers run, and the harshest landscapes traversed. Not so. Despite advances in equipment and an ever-crowded globe, some expeditions — like the winter crossing of Antarctica — continue to fail. Others, like a first descent of an isolated section of the Kuri Chu River in Bhutan, have yet to be attempted at all. So while it may be a fact that there are dwindling swaths of unexplored terrain, and "firsts" are getting harder to come by, there's still a few big ones left on humanity's bucket list. Here's the 12 we hope to see in our lifetime.