Look at a map of South America, and its cultural and environmental diversity begins to make sense. This is a continent that stretches from north of the equator to some 800 kilometers (500 miles) shy of Antarctica. Here you'll find the rain forests of the Amazon, the towering Andes, the Atacama Desert and the glaciers of Patagonia. The cultural highlights are similarly varied and fascinating. It's home to ancient Inca sites, restored Spanish-colonial towns and cosmopolitan, sophisticated cities with a European flair-Buenos Aires, Montevideo, Rio de Janeiro. Many cruises to South America also include the world's last true frontier: the frozen white continent of Antarctica.