Altar of Domitius Ahenobarbus

• 1. Introduction

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  The Altar of Domitius Ahenobarbus sits today split between two cities, with one portion in the Louvre and another in Munich's Glyptothek. Four sculpted marble plaques, carved more than two thousand years ago, depict scenes so different in style and subject that scholars long debated whether they even belonged together. One panel shows a procession of sea gods at a divine wedding. The other shows Roman officials recording names in wooden tablets, soldiers preparing for sacrifice, and a horseman waiting to march. What brought these two worlds together on a single monument? And who was the general powerful enough to promise the god Neptune a temple?

• 2. A Vow on the Water

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  Off the island of Samos, in 129 or 128 BC, a Roman commander fought a naval battle against a man named Aristonicus. Aristonicus had attempted to resist the transfer of the kingdom of Pergamon to Rome, a bequest made in the will of King Attalos III. The general who defeated him was probably Cn. Domitius Ahenobarbus. Like many Roman commanders after victory, he made a vow: build a temple to the deity who governed the sea. That vow took decades to fulfill. The actual construction of the Temple of Neptune, on the Field of Mars near the Circus Flaminius, only dates to 122 BC. That year, Cn. Domitius Ahenobarbus reached the consulship, giving him both the resources and the authority to act on his promise. The temple may rest beneath the church of Santa Maria in Publicolis, though that identification remains uncertain.

• 3. Building the Monument

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  Inside the temple's inner chamber, called the cella, stood a base measuring 5.6 metres long, 1.75 metres wide, and 0.8 metres high. Its purpose was to hold cult statues, including works attributed to the Greek sculptor Scopas. Scopas was credited with a statuary group featuring Neptune, Thetis, Achilles, the Nereids, Tritons, Phorcys, sea monsters, and other fantastic creatures. The three sides of the base originally facing the worshippers were carved in a Hellenistic style, depicting the marriage of Neptune and Amphitrite. The marble for these mythological panels was different from what was used later, drawn from Asia Minor rather than from the Greek island of Paros. Scholars believe the fourth panel, the one depicting a Roman census scene, was added after Domitius Ahenobarbus held the censorship in 115 BC. The base had to be physically moved away from the back wall to free that fourth side for carving.

• 4. The Census in Stone

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  The Louvre panel, 5.65 metres long, 0.80 metres high, and 0.015 metres thick, is carved from Parian marble. It shows the Roman census unfolding in a continuous narrative read from left to right, one of the earliest known examples of this storytelling technique in Roman art. At the far left, an official records a citizen's identity and property. The citizen holds wax tablets in one hand and stretches the other outward in the formal gesture of the oath, called the professio. The official holds a codex of two wooden tabulae on his knees; six more are stacked at his feet. His identity is debated: he wears calcei, shoes reserved for those of Senatorial rank, which may make him one of the two censors rather than a subordinate oath-taker. To the right of this scene, a censor places one hand on the shoulder of a man in a toga, completing the formal act of assigning that citizen to a social class. The citizen then points toward an infantryman, indicating the military unit to which he now belongs. The scene likely represents the censorate of Cn. Domitius Ahenobarbus and L. Caecilius Metellus in 115 BC.

• 5. Sacrifice and the Suovetaurilia

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  In the central portion of the census frieze, a religious ceremony called the lustrum takes place before an altar dedicated to Mars. The god himself stands to the left of the altar, shown in full armour. One of the two censors touches the altar with his right hand, presiding over the ritual. Three sacrificial animals are led forward: a bull, a ram, and a pig. Together they form the suovetaurilia, the traditional triple sacrifice offered to Mars to secure the army's safe departure. Young assistants called camillae help conduct the ceremony; one pours lustral water. Behind Mars, two musicians accompany the rite, one on the lyre and one on the tibia. A camillus behind the altar sings the precatio, a formal prayer. The second censor walks behind the animals, carrying a military standard called a vexillum. At the far right of the frieze, two infantrymen and a horseman with his mount close the composition, representing the four classes of infantry known as pedites and the cavalry class drawn from the aristocracy.

• 6. Neptune's Wedding Procession

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  The three mythological panels, now in Munich, show a marine thiasos: a festive procession across the sea to celebrate the marriage of Neptune and Amphitrite. At the centre, the divine couple sit in a chariot drawn by two dancing Tritons. A crowd of Nereids and Tritons surrounds them, forming their wedding retinue. To the left, a Nereid rides a sea-bull and carries a wedding present. To her right, Doris, identified in the source as the mother of Amphitrite, rides a sea-horse and holds torches in each hand to light the way. An Eros, a creature associated with Venus, accompanies her. Behind the wedding couple, another Nereid rides a hippocamp and carries a second present, accompanied by two more Erotes. The style throughout is late Hellenistic, and the material is different marble from Asia Minor rather than Parian stone, which placed the mythological panels in an entirely separate production from the census scene. A copy of the Munich piece can be seen at the Pushkin Museum in Moscow.

• 7. Lost, Found, and Divided

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  The reliefs first appear in written records in 1629 and 1631, after workers uncovered them during construction projects carried out by the Roman Santacroce family between 1598 and 1641. The family was building and expanding a palace near the Tiber, and the architect Peparelli oversaw the work. Rather than being preserved as antiques, the panels were reused as courtyard decoration. They are documented in that courtyard setting in 1683. At some point the panels were separated. The census frieze ended up at the Louvre under the catalogue number Ma 975. The mythological panels were acquired by the Glyptothek in Munich under inventory number 239. Despite the modern label of "altar," the object was never an altar. Its proper designation identifies it as a statuary group base, a platform designed to elevate and display cult statues in the cella of the Temple of Neptune. The monument makes the second oldest Roman bas-relief currently known. In 41 BC, a descendant also named Cn. Domitius Ahenobarbus had an aureus minted carrying a portrait of his ancestor on one face and a tetrastyle temple on the other, with the inscription NEPT CN DOMITIUS L F IMP, connecting the family's naval legacy to the memory of that original vow.