Vietnam's Demilitarized Zone, or DMZ, is the area around the former border between North and South Vietnam. Historically it was a narrow band of terrain extending from the Laos border to the coast, five km on either side of the Ben Hai River, roughly on the 17th parallel north latitude.
The area saw heavy fighting in the war, and ruins of old American military bases still exist. Even if you're not interested in the history, the area has some spectacular mountain scenery and rugged jungles.
While the actual border was marked by the Ben Hai river, most historical sights (i.e., American bases) are along Highway 9, which runs parallel to the river several km to the south. This road runs to the Lao border and continues onward.
The area's only major city is Dong Ha, on the coast. It's on Highway 1, and easily accessible from Hue and Da Nang. Lots of travel agents in Hue offer convenient day trips. Bus tours can be arranged just about anywhere in Hue. They are cheap at $10 to $15 per person, but be forewarned that you will have to get up very early, as the tours usually hit the road at 6 a.m. Expect to return to Hue between 6 and 7 p.m. You will also find yourself herded back on to the bus to continue to the next stop, only to find yourself waiting for some stragglers. It can get crowded in the Vinh Moc Tunnels if your bus group is large.
You can go by car, which can be expensive, but if it's raining, which is often is, you'll be glad you did. Also, private tours can bring you to some places where the big buses and large groups don't go. Tours by motorbike can be arranged, but unless you are a diehard, you may find yourself exhausted when you return, as you may cover as much as 300 km round trip. If you want a motorbike tour, it may be better to spend a night in Dong Ha, and make your arrangements there.
If you book your tour through your hotel, it will probably cost more, as the hotel takes a commission.
Unless you have your own transportation, you'll need to hire a taxi or take a guided tour to see the sights. Some local tour operators offer motorcycle trips along the Ho Chi Minh Trail.
Arranged in order from east (Vietnamese coast) to west (Lao border):
Though you'll probably encounter vendors selling GI dogtags, lighters, and other paraphernalia, you can be sure that none of them are genuinely from the war.