Curious wanderlusters should head to the island of Hainan , in the South China Sea, before it gets any more popular. The tropical isle -- with sprawling rainforest and pristine volcanic hot springs -- is a totally unexpected retreat from mainland Asia.

Hainan is the main island in China's smallest province -- once an escape for political exiles and criminals, people now flock there for the health benefits of its clean air and warm temperatures. Roughly 34 natural hot springs dot the island, and a whopping 61 percent of its area is tropical rainforest. Sanya, a city in the south, is home to sandy beaches and bays (not to mention a Ritz-Carlton hotel). Fresh fruit and fish is a staple on Hainan's menus -- dining options are rumored to include a floating seafood house and top-notch dumpling shop.