One such cave was Tham Piew, near Muang Kham.
This held well over 400 people from nearby villages, mostly women, children and older people, while the men were away at war. They would sneak out the cave entrance at night to tend the fields, which were generally decimated by the bombing and rarely produced enough food.
One day in the 1968, four US planes directed rockets at the grotto. The first three missed, but the fourth hit its target killing all inside. Today there are a number of memorials at the cave along with an interesting if graphic museum. There are counterclaims to this narrative with some insisting that the cave housed enemy fighters and that this was a legitimate military target. Whatever the case, death on a massive scale was caused here and standing at the entrance to cave and looking out over the surrounding landscape, imagining the arrival of those bombers is a sobering thought.
If you want to explore the cave past about 20m you will need to bring your own torch. The cave is located at the top of a paved walkway and set of stairs which gets your heart pumping, but is nothing that most people can't handle.
A small restaurant at the front sells cold drinks and might be able to rustle up some food if you're desperate.
It is possible to visit the cave by public songthaew, going north on the road to Sam Neua. Get off after about 4km, follow the road about 1.5 km to the foot of the hill and you'll find a steep set of stairs climbing up to the wide mouth of the cave.
If you're not interested in walking from the turn off, you could hire your own songthaew which costs 50,000 kip. If you do decide to walk, all the locals can direct you as this is a poignant part of local history and culture. There are always people tending the fields and cycling by. We found people here especially helpful and very eager to engage in help with directions.