Robotic underwater vehicles from the Monterey Bay Aquarium's Research Institute just helped discover one of the Earth's more elusive scientific treasures. Both an autonomous mapping craft and a remotely operated counterpart (which collected video and samples) traveled 12,500 feet to the bottom of Mexico's Pescadero Basin to find the Pacific's deepest hot hydrothermal vents. The machines achieved their feat in just two days, versus the years that it'd take for conventional undersea mapping -- and they achieved the kind of detail that would likely be difficult or impossible using those earlier techniques.
You definitely wouldn't want to visit in person, even in a craft that could survive the crushing pressure at these depths. Giant chimneys around the vents spew super-hot (660F) metallic fluids, and the only forms of life nearby are tubeworms and other critters whose symbiotic bacteria turns the vents' toxic chemicals into sustenance. In other words, it's not exactly a tourist attraction -- robots are likely the closest you'll get to a human presence in this unforgiving landscape.