Ok now turn right and walk down the Via Sacra towards the 'Arch of Septimius Severus'. About 3/4 of the way down the 'Portico of Gaius and Lucius Caesar' just on the other side of the short fence you will come across a marble circle ring (2.4 m diameter) flush with the ground with a small stone plaque (in Italian) alongside it. Here's a photo. This Shrine marks the spot where the 'Cloaca Maxima' (Great Drain/Sewer) enters the Roman Forum.
Romans even in Julius Caesar's day didn't know the real origins or actual purpose of this shrine. Traditionally (legend, myth) it goes back to Romulus' co-ruling King 'Titus Tatius' founding this cult and shrine. According to Livy, Cloacina was one of the titles of Venus. This name comes from the verb "cluere" (to purify or cleanse). The myth of the foundation of her shrine is related to the Roman-Sabine War. Pliny: At the time of the foundation of Rome myrtles (evergreen shrub, nice aroma) grew here. Before going into battle because of the Rape of the Sabine Women both sides laid down their arms and purified themselves with the myrtle. At that time a river/stream flowed through the Forum which marked the boundary between these two warring peoples. Centuries later a coin seems to show one statue in the shrine holding a *myrtle* branch and the other a sword. So it seems that this myth or fact about this shrine does go back to Romulus' time (i.e. Myrtle Branch). But they are fairly certain that originally it does go back to at least the first phase of the 'Cloacina Maxima' open canal (early 600 BC?). When this shrine was dedicated simply to 'Cloacina' (Sacrum Cloacina) which was the divinity of the 'Cloaca' as in 'Cloaca Maxima'. Over time the shrine somehow became identified with Venus and called 'Venus Cloacina'.
It was an open-air circular shrine with two female cult statues (Venus and Cloacina) standing atop it enclosed by a short metal balustrade (fence). It rests directly over the stone vaulted 'Cloaca Maxima' in eight layers of stone. The first layers were to probably bring it up to ground level when the Cloaca Maxima was built, the other layers were to keep it at ground level as the Forum level rose due to over-paving the Forum Square, the Via Sacra and buildings being rebuilt over earlier ones (The marble ring, the Forum Square and the section of the Via Sacra you are standing on dates to Augustus' era 2000 years ago). The nearby plaque (in Italian) tells the story of a Father's honor killing of his daughter at this location in 451 BC.
For more information and photos, please see Shrine of Venus Cloacina in A Tourist in Rome.Next: #5: Temple of Janus