Named by French colonists, the stunning Tonkin coast -- which extends from Haiphong and Halong Bay all the way to central Vietnam -- will forever be associated with the disputed artillery exchange between U.S. and Vietnamese ships that took place in the Gulf of Tonkin. The altercation ultimately led to the Tonkin Resolution and opened the door on the whole Vietnam shootin' match. What puts this region on the map these days, though, is the likelihood that the sneakers or sandals you're wearing, or the shirt on your back, were put together in one of the large factories that line the road between Hanoi and the sea.
Boat tours of the UNESCO World Heritage Site Halong Bay, with its legendary limestone peaks and miles of calm waters, are the highlight. The small city of Haiphong has its own colonial-throwback kind of charm, and little Cat Ba Island, with its national park, is commonly included in itineraries with Halong Bay. You can also now reach Cat Ba by high-speed ferry from Hanoi.
There are also some good "off the map" destinations in this region, including Bai Thu Long Bay, just north of Halong (best visited on an organized tour), and Do Son Beach, just south of Haiphong. The Tonkin Coast area is just a few short hours by good road from Hanoi, and an overnight should suffice to experience any of these stops. Just about anybody in Hanoi sells tours to Halong and Cat Ba, with service ranging from Hanoi's ultrabudget-traveler cafe trips on old, beat-up junk boats, to luxurious packages such as the Jewel of the Bay and the Emeraude, a replica of an old colonial steamer.