The entrance is small enough to make you duck.
Inside, the light changes. The ochre walls give way to deep reds, faded blues, and the brown-black of centuries-old pigment. A figure emerges from the gloom: Christ, perhaps, or one of the apostles. Above him, another scene. Below, another. The ceiling is painted too, and the walls, and the curve of the apse. For a moment, the strange volcanic landscape outside seems very far away.