Waaay down under.

• Position: New & Trends - Son Doong Cave in Vietnam - Brief article

It's five-and-a-half miles long, has its own river and jungle, and could fit a 40-story skyscraper within its walls. And now the biggest cave in the world--first explored by British scientists in 2009-has opened for business in Vietnam. Six tourists from the U.S., Russia, Australia, and Norway recently spent a week exploring and camping out in the Son Doong cave, which formed 2.5 million years ago. Laser...