The Musanze Caves, a short drive from the town centre, are a lava tube system formed by volcanic activity in the Virunga chain — the solidified crust of a lava flow that left a hollow tunnel underground when the interior continued to flow and drain away. The caves extend for about two kilometres and include cathedral-sized chambers, narrow crawlways, and a small underground lake. Bat colonies inhabit some sections; the caves also hold archaeological evidence of early human habitation.
The caves are managed as a tourist site with guides and basic lighting. Tours take about an hour and require you to crouch in some passages and navigate uneven surfaces; sturdy shoes are recommended. The site is less visited than the national park attractions but provides an interesting perspective on the volcanic geology that created the Virunga landscape. The cave entrance is surrounded by secondary forest, and the approach road passes through agricultural land typical of the densely farmed northern Rwanda plateau.