The theatre of Andromeda, which is next to the water tower, has been documented since 1673. This name began to appear in the 18th century though it was completely inappropriate because then, as now, it did not bear any statue dedicated to the goddess. The theatre is accessed through a cobblestone driveway consisting of a tuff stone structure with a centre containing a rectangular niche with an arched closure, which in turn contains a smaller niche with a smaller female sculpture. The statue portrays a winged woman defined by sources as a mermaid with a monstrous mask. The woman, whose face is almost expressionless, holds her breasts where one can glimpse pipe holes where once jets of water poured out.
The same large mask of a face with vaguely human traits but more like a lioness and which sprayed out water from its mouth, was part of this group of sculptures made in white marble. Under the group of sculptures is a high rectangular basin that was used to collect the water. Together with the female sculpture, it formed a small fountain.
In the upper part of the theatre there are still a few visible decorations, some of which are not in perfect condition. Some decorative items, in fact, now seem hopelessly lost. What have survived and which flank the main decoration, are vases with handles and bases, are but devoid of their original colours and very damaged. These are positioned in the centre of the theatre, which corresponds to the niche below.
As the theatre of Andromeda waits for restoration, we can still get a glimpse of the orange colour of the interior of the niche as well as parts of the frescoes that decorated it in past centuries. In fact, in the upper most portions we can observe a mixtilinear motif in the vaults that dialogue with the decoration surrounding the small niche with the mermaid. Next to the sculpture, however, the fading paint reveals the presence of the older painted decorations in blue and red motifs, which vaguely resemble candelabras with scrolls. The floor below is made up of small river pebbles surrounding water tubes that created more water features.