Halong bay is the most scenic spot in northern Vietnam as one of the listed UNESCO Word Heritage Site. The awesome rock and limestone caves are one of the wonders in the world too that you should not be missed !
If you are not prepare to be on long journey trip, which is 3-4 hours drive to Hanoi, then discovering the bay for its karst landscape by sailing on the traditional cruise. Cruising among the limestone rocks and islets of Halong Bay, enjoying the inspiring scenery are awesome !
You may consider to take a 45minutes ferry ride to Cat Ba Island for day trip.