Halong Bay, Vietnam is a mesmerizing place. Recently named as one of the new seven natural wonders of the world, the ghostly peaks are shrouded in fog and fade in and out of sight. Located in the northeast corner of Vietnam, visiting the trio of Hanoi, Halong Bay and Sapa was a highlight of my recent two months in Asia - and one I recommend to you.
To get there, the best mile redemptions for U.S. residents are to Hanoi with United Airlines. 80,000 United miles will get you a round-trip ticket in economy or 160,000 in business class. Expect to pay around $30 in booking fees. Note that a similar amount of American Airlines miles can be used, but you must call to book on a partner airline.
Note that once you get to Hanoi, there are a number of options to go to Halong Bay. Most travel by chartered tour bus that include a boat ride around the bay. I recommend Paradise Cruises if you take this route. For more independent travelers, you can book a private car transfer and your own boat ride for a larger fee. Just don't forget to get a visa.