Illuminated to the right of the ditch is the mouth of a pentagonal cross-section sewer from the Roman period running underground east-west (from the Cathedral to the river).

This is the outlet of a large pipe covered with a stone and mortar vault which drained wastewater and rainwater from the higher parts of the city. As is often the case in Roman cities with a robust and complex sewage system, the sewer was reused in the Andalusian period.