A relatively deep and narrow linear feature, aligned more or less with the Via Gabina to the north and the northern wall of Room 8 to the east, a structure which the cut appears to respect. Its function is uncertain (possibly drainage?), but at the very least it relates to the anomalous presence of the otherwise unworked surrounding bedrock in this part of the city. The reason why this area seems to have been unoccupied and the bedrock was left relatively unworked remains an important open question.