With a region as varied as South America, it's hard to know where to begin. Amazon River cruises bring you close to the rainforest and the indigenous people who live there. The Galapagos Islands off of Ecuador are a must-do for outdoor lovers; add a trek to Machu Picchu before or after. And finally, a Round-the-Horn cruise takes passengers from Brazil south to the tip of Argentina before exploring the fjords of Chile.