As early as the middle of the VIII century B.C., this area was taken over by merchants, in time mainly those who dealt in cattle (thus the name “cattle market”). It is here that deep-sea vessels docked at the first and oldest of Roman ports (Portus Tiberinus). It was not until the III century B.C., that it was moved to Ostia, while Portus Tiberinus became an unloading dock for smaller ships coming from there. It operated until the II century A.D, when during the reign of Emperor Trajan it was closed, and the area was used for warehouses.

Significant temples were built at Forum Boarium, including a sanctuary to Hercules, who enjoyed particular reverence here and who according to a legend was to defeat Cacus here, a three-headed monster who at the time threatened the inhabitants of the area. For freeing the populace from this threat, in gratitude, the hero received an altar (Ara Maxima). Hercules rapidly became a patron deity of the city, its leaders, but most of all merchants, bankers and traders, who cared for their interests here. The form of the offering to Hercules also contributed to business contacts – it had to be given only in natural form, mainly as sacrificial animals, while their dead bodies were to be eaten on the spot. These celebrations were often attended by hundreds of invited guests. The feasts were accompanied by games, such as the ones organized in 264 B.C., when on a makeshift wooden arena first gladiator fights in Rome, were organized.

The Ara Maxima altar had been reconstructed and modernized numerous times, until it fell victim to the great fire during the reign of Emperor Nero. It was however, rebuilt and existed until the IV century, when it was finally torn down, while other buildings were put up on its foundations, including the Church of Santa Maria in Cosmedin. The remains of the platform, upon which the altar stood can today be seen in the crypt of this very church, while the altar itself is only referred to in the name of one of the streets (via dell’Ara Maxima di Ercole), which runs through the place where it was located.

The round temple, decorated with a row of sleek Ionic columns, erected next to the altar, was also devoted to Hercules and it still stands today. It is part of a group of the oldest buildings of ancient Rome. Hercules Olivarius was worshiped within, but it is also known as the Temple of Hercules Victor. Its construction is dated as II century B.C. A gilded statue of the hero excavated at Forum Boarium in the XV century, which today is found at the Capitoline Hill (Musei Capitolini) must be connected to one of the two buildings. A second temple, preserved in its original form, was built here as early as IV century B.C., a rectangular building, situated on a high podium, the Temple of Portunus, was devoted to the god of Tiber and the port.

The boundary of Forum Boarium from the southeastern side was made up of the house of the prefect, the so-called Cura Annonae, meaning office of city food supply, or more appropriately   grain supply; its remains can also be found in the Church of Santa Maria in Cosmedin.

Other buildings which must not be forgotten and which are found here are the Arch of the Silversmiths (Arco degli Argentari), built at the beginning of the III century A.D. and the Arch of Janus, built a full century later, a roofed place of trade meetings (Janus Quadrifrons). These, along with Circus Maximus, marked the northern boundary of the Forum.