SU 5819 is part of an arch feature on the southeastern corner of Room 22, the northern portion if which is physically separate and was documented as SU 5820. It was probably built when the room was repurposed as a taberna, which is a working interpretation of the space. The space under the arch may have been used as for storage while perhaps supporting an additional counter or shelf above. Unfortunately, most of the arch was not preserved and the Soprintendenza had previously excavated the area, meaning that not much evidence that could point to the arch's specific function has been found.