Sewer?

The channel was detected below SU 1203 and since it is covered with tufo slabs and sits right below the southern edge of the section the possibility of encountering it was rather limited. We were able to peer into the channel and it is certain that we found the wasternmost edge of it. A large pit (SU 1229) was excavated in order to reach the bedrock. During the excavation of this starting pit for the construction of the channel the earlier floor (SU 1173) was destroyed. The chronology of the impact is quite clear, but not the date. Whilst peering into the channel one could see a T-junction meaning another channel crossing our SU 1228. One could see light falling into this cross-channel from SW direction and could also feel very fresh and cold air streaming through the channel. The channel was dug as an open cut into the bedrock and covered afterwards with tufo slabs. Is I would be much smaller I would have crouched into it to find out more about it. Interpretation: sewer?