Sometimes, it's hard to imagine that there are any truly far-flung corners on this planet left for travelers anymore. After all, there are hotels undersea and plans to send tourists into outer space. But intrepid types need not worry. From glass igloos in remote Iceland to a cave in the American Southwest, GAYOT's list of Top 10 Extreme Hotels Worldwide promises adventure. Whether you scuba dive to your front door or reach it by way of a hanging bridge, we think you'll be impressed by the ingenuity, originality and yes, even luxury, offered by these singular properties.