Forum Boarium
Discover Forum Boarium
Last updated on October 6, 2026Introduction
The Foro Boario was the area given over to the cattle market, lying between the Tiber, the Capitol, the Palatine and the Aventine.
Legend puts the start of Rome here. According to it, Hercules, having arrived in the area of the foro Boario with the oxen of Geryon, was robbed of them by the giant Cacus, who lived in a cave on the slopes of the Aventine. After killing the giant, Hercules was honoured as a god by the ancient inhabitants of the Palatine, the Arcadians, who dedicated an altar to him, the Ara Maxima — and this altar, of which the tufa core is preserved, is inside the church of Santa Maria in Cosmedin.
It was a swamp before it was anything. The area, occupied in ancient times by the marsh of the Velabro, was drained by the Etruscan kings in the 6th century BC with the construction of the Cloaca Maxima, of which the remains of the arches are still visible. Also in the 6th century BC, the establishment of the Porto Tiberino — which extended where the offices of the Anagrafe now stand — is attributed to Servius Tullius.
Two republican temples still face the river. The first and older one, of rectangular plan, dedicated to the river divinity Portunus, and the second, of circular plan, dedicated to Hercules Victor.
And the empire added three more monuments. In the imperial age came the warehouses by the river port of the Trajanic age (98-117 AD), the Arco degli Argentari, an elegant work of the Severan age (204 AD), and the four-fronted arch of Janus, an imposing construction probably of the time of Constantius II (337-361 AD).
Architecture
Two republican temples define it, and they are opposites. Turismo Roma records that the two temples towards the Tiber date from the republican period: the first, more ancient, of rectangular plan, dedicated to the river divinity Portunus, and the second, of circular plan, dedicated to Hercules Victor.
Its oldest architecture is drainage. The Cloaca Maxima, built by the Etruscan kings in the 6th century BC to drain the marsh of the Velabro, survives as the remains of its arches.
A river port shaped the area too. The Porto Tiberino, attributed to Servius Tullius, extended where the offices of the Anagrafe now stand, and the imperial age added warehouses by the river port of the Trajanic age.
Two arches close the sequence. The Arco degli Argentari, an elegant work of the Severan age, 204 AD, and the four-fronted arch of Janus, an imposing construction probably of the time of Constantius II.
And one altar is embedded in a later building. The Ara Maxima survives as its tufa core, inside the church of Santa Maria in Cosmedin.
How it was built and evolved over time
Nothing could be built until the water was taken away. The area was occupied in ancient times by the marsh of the Velabro and was drained by the Etruscan kings in the 6th century BC with the construction of the Cloaca Maxima. Every later monument here stands on that decision.
The river came next. The Porto Tiberino, attributed to Servius Tullius in the same century, gave the drained ground a purpose and the market its traffic.
The temples went up in the republic, in two different shapes. A rectangular one for Portunus and a circular one for Hercules Victor, both towards the Tiber.
The empire built in bulk and then in display. First the warehouses by the river port of the Trajanic age (98-117 AD) — working buildings — then the Arco degli Argentari (204 AD) and the four-fronted Janus, probably under Constantius II (337-361 AD).
And the altar was built around rather than replaced. The Ara Maxima, dedicated by the Arcadians, kept its tufa core inside what became Santa Maria in Cosmedin.
Frequently asked questions
Is there a charge? No. Turismo Roma publishes no price and no ticket link for the Foro Boario.
What are the opening hours? None are published. It is an open archaeological area in the street grid.
What was the Forum Boarium? The area given over to the cattle market, between the Tiber, the Capitol, the Palatine and the Aventine.
What is the Hercules story? That Hercules, arriving with the oxen of Geryon, was robbed of them by the giant Cacus, who lived in a cave on the slopes of the Aventine; after killing him, Hercules was honoured as a god by the Arcadians, who dedicated to him an altar, the Ara Maxima.
Where is the Ara Maxima now? Its tufa core is preserved inside the church of Santa Maria in Cosmedin.
What are the two temples? The first and older, of rectangular plan, dedicated to the river divinity Portunus, and the second, of circular plan, dedicated to Hercules Victor. Both are of the republican age.
Why was the ground drained? Because it was occupied in ancient times by the marsh of the Velabro; the Etruscan kings drained it in the 6th century BC with the construction of the Cloaca Maxima.
Can you see the Cloaca Maxima? Yes — the remains of the arches are still visible.
What was the Porto Tiberino? A river port attributed to Servius Tullius in the 6th century BC, which extended where the offices of the Anagrafe now stand.
What are the two arches? The Arco degli Argentari, an elegant work of the Severan age (204 AD), and the four-fronted arch of Janus, probably of the time of Constantius II (337-361 AD).
Can I go inside the temples? Nothing about entering them is published; they are read from the public space around them.