This cut seems to have been made for two purposes: firstly, for the construction of the cuniculus, at least 10-12 feet deep (sounding), of which only the northwest corner is visible under tufo blocks 5397. Presumably this cuniculus connects to the other deep bedrock-cut drainage tunnels known in this sector ,and facilitated the drainage of the lower terrace of the complex. After the cutting of the cuniculus, this cut served as the foundation trench for blocks 5397, which mostly cover the cuniculus, although it seems that their position would still have allowed for water to drain down here; the blocks sit on the 'shelf' formed by the middle step in the cut. Presumably the whole - blocks and cut - were covered by tufo slab floor 5410. Because of the purpose of the cut (drainage) and the way in which the northernmost block of 5397 broke and collapsed, this cut seems to have remained mostly empty until the removal of the slab floor, after which alluvial deposits (5378) filled it.