A type of tomb that was widely used within the catacombs of Rome in the 3rd century AD. The word itself is derived from arcus "arch" and solium "throne", used in the same sense as "sarcophagus". An arcosolium was basically a recess used to frame a coffin, created by excavating an arch-topped niche into the tufa wall. The bottom of the recess was higher than the floor, and the inside was sometimes decorated with symbolic frescos, depending on the status of the dececed. In some instances, as in the crypt of Saint Januarius, the front wall of the arcosolium tomb was constructed of masonry. A more ancient form of arcosolium is an arched niche of a smaller scale, excavated to the level of the floor, into which was slid a sarcophagus, typically made of terracotta.