What material are catacombs made of?

Catacombs are typically constructed from soft, easily quarried materials such as limestone, volcanic rock, or tuff. These materials allow for the creation of extensive underground networks through excavation. In many historical catacombs, the walls are often lined with niches for burial, and the overall structure is designed to accommodate the interment of multiple remains. The choice of material often reflects the geological characteristics of the region where the catacombs are located.