The Baths of the Jealous One were built c. 50 AD (opus reticulatum). Modifications have been dated to the period of Antoninus Pius (opus latericium). The paintings and black-and-white mosaics have been dated to the first half of the third century. The latest masonry in the building belongs to the early fifth century.

To the north of fish shops V,V,1 is vestibule A, that was reached from the Semita dei Cippi through a porticus. On the floor is a mosaic with a marine scene. To the east of the fish shops is another vestibule, reached from Via dell'Invidioso (B). Here is a mosaic with a Nereid on a hippocamp. Room C was a dressing room (apodyterium). In the south and west wall, belonging to the first phase, the niches can be seen in which the clothes were put away. The niches were later blocked with bricks.

Room D was a cold bath (frigidarium), with apses with basins in the south and east part. On the floor is a mosaic of an amorino riding a marine tiger. The apse in the east part has a large window giving onto Via del Sole, that is partly blocked by the apse. It was built in the last quarter of the third century. Further to the north are the heated rooms (E, F, G, H), that were modified in the first quarter of the fifth century. To the west is the palaestra (J). The palaestra could also be reached from the Decumanus Maximus, through corridor K.

Room L was a bar, that could be reached from the street (Via del Sole) and the apodyterium. The bar counter is in the north-east corner. In the east wall is a filled in cult niche. In the south-east corner of the block (M) were basins and waterwheels. On the north wall of M is a drip stone, as seen in caves.

Three brick piers were set against the south facade. Behind the westernmost one are a few strange decorative elements, from bottom to top:
- A curved row of yellow bricks. The surface is smooth.
- A horizontal row of yellow bricks with a rounded surface.
- Above that a triangular yellow brick, or rather a brick placed vertically instead of horizontally.
- Next to that a rod with two incised lines at the upper end, and a more or less square top with an incised X.
- Above the brick and the rod an incomplete yellow brick frame with a painted red band.
- Inside the frame, to the right, a fragment of a relief.
- Inside the frame, to the left, a relief of a phallus with a curved end and a plummet. During a restoration in 1991 this relief was placed upside-down in the wall. What is more, a missing part of the relief appeared after the restoration, suggesting that what is seen today in situ is a modern cast (cf. the replacement of the relief of a snake in the Piccolo Mercato). In December 2007 Stephan Mols suggested on the Ostia mailing list that the phallus is in reality a woodworker's tool, in German a so-called Ascia-Hobel (see Gaitzsch, Eiserne römische Werkzeuge, Oxford 1980, 38-46), translated an "adze-plane".
In antiquity all of this was later tampered with and clearly covered with plaster.