After Hoi An I spent two nights in Hue, a four or five-hour bus journey north from Hoi An. I'm having to do my stops quite quickly as I'm squeezing Vietnam into two weeks in order to fit a few days in Luang Prabang in at the end of my trip. Considering my feelings towards this country I'm quite glad I only budgeted two weeks here. If I hadn't booked my flight to Laos already to make sure the price didn't go up, I probably would've shot out and spent more time in Laos. I did decide not to visit Da Lat, the Mekong Delta, and the beach resorts of Nha Trang and Mui Ne, however, so I can't comment on them.
Hue is... okay. It's a relatively happening city, but in terms of sights it's limited to the Citadel in the city centre (like a toy version of Beijing's Forbidden City) and the mausoleums on the outskirts. Many travellers skip Hue altogether, but I was keen to see the Demilitarised Zone (DMZ) that is easily reachable by day tour from Hue.
The DMZ was a stretch of land that divided north and south Vietnam during the American War. It was the scene of a lot of bloodshed and bombing, and is also home to the Vinh Moc tunnels, an underground system of passageways that villagers lived in for six years, complete with family rooms, maternity rooms, toilets and a meeting room. It's spread across three levels between 12 and 23m below ground. It's more spacious and less claustrophobic than the Cu Chi tunnels in the south.
The tour cost $17, although you might be able to find it cheaper if you shop around. It was interesting, but only just worth the amount of driving. It was a 12 hour day, and around six hours of that was sitting on the bus.
The next day I took the bus back to Da Nang to catch my flight up to Hanoi. It's so much cheaper to fly from Da Nang than from Hue, so the $4 bus journey and $5 taxi from the city to the airport is definitely worth it if you have the time and want to save around $80 on the flight ticket.
Incidentally, Vietnam's sleeping buses are relatively comfortable. You can get open-tour bus tickets between popular destinations and effectively hop-on and hop-off as you traverse the length of the country. You get an individual seat/bed that reclines and has space for a small bag or your shoes under the headrest. The back is less comfortable though, with two layers of five beds side by side with no barrier between them. There's also less room to move around. So if you can, ask for a seat towards the front of the bus to avoid being crammed in with strangers at the back.