The so-called Cave of Fates was originally a natural cave wich around the middle 2nd century BC was framed in a structure of tuff blocks and at the end of the same century was included in the complex of Forum. Splendid mosaic decoration (Mosaic of Pisces) dating back at the end of 2nd century BC, was unfortunately damaged by subsequent reuses of the its environment as a place for lime production.
The Mosaic of Pisces represents the seabed inhabited by fishes and shellfishes. It is also visible a part of shore along which the waves break, made in white lines, the color of the sea is clearer near the coast and gets darker and bluer towards the bottom of the cave obtaining the impression of the abyssal depths.The fishes are represented in an inverted perspective, those further away from the observer are larger in size. The details are made with amazing almost scientific precision. At the bottom on the right there is the scene of sacrifice to Neptune that seems to take place in the port of Alexandria in Egypt, since the shape of the altar and column capitals represented are typically Alexandrians.
The Mosaic of Piesces is one of the most remarkable Hellenistic mosaics, compared to some examples from Rome and Pompeii, that have same sea subject, and also, like the Mosaic of Nile, can be attributed to artists of Alexandria who worked on site in the same period (late 2nd century BC).