The House of the Fishes has two main building phases, that have been dated to the middle and the last quarter of the third century AD.

Click here to open a detailed plan of the house in a new window (from Heres 1982, fig. 87).

A few treads lead to vestibule A. The walls of the vestibule were painted. On the floor is a white mosaic with a polychrome panel: a chalice with a fish, and two fishes next to the stem of the chalice. These may well have been Christian symbols, an interpretation that is not universally accepted, however. The panel was seen properly when people left the building, which suggests that it was a farewell greeting for Christians who had met in the house. In the passage to room B are marble treads flanked by brick semi-columns.

On the walls of room B is plaster, on the floor a white mosaic. A wide passage leads to the porticus of courtyard G. The room is flanked by rooms C and F. In F are remains of plaster. C was much more luxurious. It is reached along marble treads from the porticus, and there is marble on the floor and lower part of the walls. In the walls are pipes for heating the room. The oven was in room D. The adjacent room E is a cistern.

The porticus is U-shaped. The floor is decorated with a black-and-white geometric mosaic. Between the piers in front of rooms O, Q and R low walls were built, with benches on the side of the porticus. At one end of the porticus is room H, with polychrome opus sectile of very high quality.

Courtyard G was reached through a wide passage in front of room B. On the floor of the courtyard is a black-and-white mosaic. In the centre is a square marble basin, with a tiny pyramid with small treads, along which water flowed from the top. Later a large semicircular basin was added. It has a marble floor, in the centre of which a disc and a dolphin were depicted (no longer in situ). The dolphin may have been another Christian symbol. Another marble fountain was set against the back wall of the courtyard. In front is a basin, on top a semicircular painted niche for a statue. A marble threshold leads to room I, with a coarse mosaic. In the courtyard a small statue was found of Fortuna with cornucopiae.

On the opposite side of the courtyard is the large hall N. In the entrance are two marble columns and two brick semi-columns. Between the columns is a marble threshold, between the columns and the semi-columns are low walls. The lower part of the walls of the room was covered with marble. On the floor is a black-and-white mosaic of very high quality, consisting of many small panels with geometric motifs. One of the panels has a depiction of a trident and two fishes. Next to the hall is room M, with a raised floor and heating pipes along one wall. It was heated from the tiny room L. On the other side of N is room P, that is flanked by an external staircase and an independent shop.

In the entrances to rooms Q and R are marble thresholds. In room R is a brick staircase, which replaced a staircase with travertine treads, reached from room S.