The karst seascape of Halong Bay is one of the world's most spellbinding sea views and is a UNESCO World Heritage Site. Thousands of limestone islands sit within this bay in the Gulf of Tonkin, eroded into jagged pinnacles by wind and water action over millennia. With the bay's scenery best seen by boat, this is prime cruising territory. Opt for at least an overnight tour to see Halong Bay's iconic views as a day trip doesn't do it justice. There are plenty of caves in the bay that can be entered including the Hang Sung Sot, with three mammoth caverns, and the Hang Dao Go, with superbly weird stalagmites and stalactites. For most people though, the highlight is simply cruising amid the karsts and soaking up the changing scenery of pinnacles as you pass by.
