Halong bay is one of 7 natural wonders in the world and a world heritage site in vietnam a visit here is a must for any trip to vietnam with almost 2 000 islands rising from the emerald water of the gulf of tonkin halong is an excellent example of a karst landscape and it is easy to see why it is one of the 7 natural wonders of the world this overnight trip allows you to see all of what is best of this beautiful area