The Elephant Springs, some 53 kilometres from Hue, is an excellent natural spring that is well worth a visit.
Particularly on a hot day, the natural pool below a small waterfall makes for a very refreshing dip. You can sluice yourself down the smooth rocks at the base of the falls, and there are plenty more spots upstream to explore.
The place can be pretty deserted on weekdays and during off season, which is great if you're looking for some privacy, but not so great in terms of getting some food and drinks -- the food stalls around the springs are only open on peak days. When they are, you can enjoy a cold beer and munch on a scraggy boiled chicken while you're wallowing in the water. When the stalls aren't open, it makes sense to pack a lunch and BYO.
It's not too hard to get to, but it's not well-marked, and it might make sense to hook up with a guide -- most of the motorcycle taxi drivers know where it is. They can also help you sort out the food and drink situation.
How to get there
To get there, take Highway One south out of Hue, and keep an eye on the mile markers along the road. When you get to the one that says Danang 52km you're there (coming from the other direction, it says P. Bai 44km). Take a right and follow the road across the stream to the springs (resist taking a left across the big bridge -- go straight and the road veers left over the stream.) Admission is free, plus 5,000 VND to park your motorbike.
The Travelfish newsletter is sent out every Monday and is jammed full of free advice for travel in Southeast Asia. You can see past issues here.