Hue tours are built around one walled city and the tombs along the river below it, which is a tighter day than most Vietnamese destinations offer. Hue was the imperial capital under the Nguyen dynasty from 1802: a citadel with the Forbidden Purple City inside it, royal tombs strung along the Perfume River, and the sharpest food in the country. Da Nang is about 100 km south over the Hai Van Pass, which is why most itineraries put a hotel there and take Hue as a day. What a tour handles here is distance and choice. The tombs are spread out along the river south of the city, far enough apart that a taxi day turns into four separate negotiations, and the Citadel rewards a guide because the layout only makes sense once someone explains what was demolished and when. Hue also sits on every north-to-central route: the multi-day packages that run Hanoi to Ha Long Bay and down the central coast carry the transport and the hotels between cities, priced per person by hotel class over six days or more. One day or two is the question. A single day covers the Citadel and one tomb properly, and that is the version most people take from Da Nang. Two days adds a second tomb, Thien Mu Pagoda and a boat on the Perfume River, and gives you an evening for the food, which is the argument for sleeping here rather than driving back. On timing, February to July is the driest stretch and March to May the most comfortable; October and November carry the heaviest storm and flood exposure on this coast, so avoid that window if your plan depends on being outdoors.