The emerald green waters of Halong Bay, a Unesco World Heritage site about 165km east of Hanoi, are flecked with around 1,600 towering limeston islets formed over millions of years.Halong Bay, which means "bay of descending dragon", is one of Asia's travel hotspots and attracts around 6 million visitors every year. The best way to navigate Halong Bay is by taking an overnight junk boat tour.