Located on the west wall of the rear garden was a nymphaeum. This took the form of an aedicula structure with a large asped niche in its eastern face. The structure was entirely decorated with colourful glass tesserae and shells, which were made up of various alternating bands of geometric patterns present across the façade. Within the niche, on the back wall, was a depiction of Sarnus surrounded by reeds. Just below his head was a small opening from which water fell onto marble steps into an apsidal pool below. The vault of the niche was decorated in a shell pattern, with a vase present in the centre. On the façade of the fountain, flanking the base of the opening of the niche, were two masks with open mouths which have been suggested to have once held lamps. At the top of the façade, below the pediment and flanking either side of the niche were two swans. Shells were used to outline sections of mosaic decoration. The pool at the front of the structure was painted blue on its interior and was completed in marble.