The cut seems to have been made in order to access a drainage channel that continues diagonally below Room 22 (a hole was found in the middle of the room) and back into Room 21. The cut exposes large stone slabs that were used to cover the drainage channel as well as smaller holes, located along the southern edge of the cut and following its semicircular shape. The slabs extend beneath floor surfaces to the south and the wall to the north. Some mortar is preserved in places between slabs, and the cut may have been made to allow for these repairs/modifications The western part of the cut gives way to bedrock at the bottom, which is good support for the tufo slabs.