A century ago, a majority of the planet's residents never managed to make it further than a few hundred miles from their birthplaces. Now, with one billion international arrivals a year, travelers are spreading into the last unexplored corners of the globe. The demand for bigger, better, and more adventurous experiences is skyrocketing. "There's an accessibility that there never was before, and people can do things that were once unimaginable," says Shannon Stowell, president of the Adventure Travel Trade Association. "If you can think of it and Google it, there's probably someone who can take you."
Here are nine of the most extreme trips on the planet - and the outfitters that take adventurers over the edge and back again.