About an hour by songthaew from Sam Neua is the neat and tidy town of Vieng Xai, set among beautiful karst limestone mountains that rise out of the rice fields like hulking monoliths.
During the Secret War this area was the seat of command for the most powerful members of the Pathet Lao, the nationalist party that won the war and now runs the country. The caves are the major reason for visiting Vieng Xai, either staying overnight or travelling as part of a package from Sam Neua.
It's not possible to see the caves without a government guide, so you'll need to swing by Vieng Xai Cave Visitor Centre, just past the centre of town heading toward the largest limestone mountains.
Done on foot, or bicycle if you can convince others in the group to hire, and with a guide of reasonable English-speaking ability, the tour takes you into the caves of the most important government leaders, including Prince Souvannaphoum and the venerated Kaysone. The dank, dark rooms are a stark reminder of the hardships these people were prepared to endure to fight for their country.
Freestanding houses at the entrances to each cave, in use from when the bombing stopped in 1972-3 until the capital was established in Vientiane in 1979, merely reinforce how suffocating it must have been to live enclosed by concrete for all those years.
There are no internet cafes in town, but there is a post office and 3G internet through Unitel.
Money can be changed at the bank across the road and down the hill from the bus station during business hours and there is an ATM in town at the market.
By Adam Poskitt.