The Ancient Romans Had a Strange Ritual After Thunderstorms

Outside of Rome, archaeologists excavating at Hadrian’s Villa have unearthed a rare marble slab bearing an inscription that provides a new understanding of the religious rituals that took place in the ancient retreat built in the second century A.D. by Roman Emperor Hadrian. It reads FVLGVR SVBMANIVM—the “lightning bolt of Summanus,” god of nocturnal lightning—indicating that the UNESCO World Heritage site was the spot of an ancient lightning strike.

The discovery was made during excavations conducted by the Department of Humanities (DISTUM) of the University of Urbino Carlo Bo, under a concession from the Italian Ministry of Culture and directed by professor Fabio Giorgio Cavallero.  

“In Roman belief, a place struck by lightning was immediately considered religiosus, having been consecrated by the deity itself,” says Alberto Samonà, the director of the Istituto Villa Adriana and the Villa d’Este, which collaborated on the excavation. “The traces left by the lightning were ritually collected and buried, accompanied by appropriate rites and sacrifices.”

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Lightning had power to convert profane spaces into sacred ones because it was a sign of communication from the gods. Elizabeth Meyer, an ancient historian and expert in inscriptions at the University of Virginia, explains that Romans as well as the nearby Etruscans believed the heavens were a space for constant contact between gods and humans. Certain signs from the sky—such as crows, owls, or shooting stars—were deciphered by priests as omens that foretold their future and fortune. Romans specifically relied on priests called haruspices to interpret extreme weather like lightning, which was particularly associated with Jupiter and with his nighttime counterpart, Summanus.

“Since the inscription invokes Summanus, whom ancient sources associate with nocturnal lightning, it records a lightning strike that occurred during the night,” Samonà says.

After the burial of objects struck by a bolt, Romans would mark off the boundary zone of this newly sacralized space with an enclosure called a bidental, a term that “derives from the sacrifice of a two-year-old sheep (ovis bima), offered during the consecration ritual,” Samonà explains. An altar or base embedded with the inscription—called a fulgur conditum, or “buried lightning” inscription—was then placed at the bottom of the enclosure.

The new enclosure discovered in the area of the amphitheater likely dates to the Hadrianic period, between A.D. 117 and 138. There are other recorded instances of lightning strikes that resulted in the need to bury objects and create the small shrine overtop of it. However, only around 50 of these inscriptions survive today, making the new find at Hadrian’s Villa an important discovery.  The inscription confirms much of what we already knew about Roman religious reactions to lightning, but also allows archaeologists to better reconstruct the religious rites and ritual that took place at the famed villa.

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As the excavations at the amphitheater site continue, Samonà notes, the archaeologists will attempt to find out what happened to the original building struck by lightning. There is still a question of whether it was torn down and buried or suffered a different fate.

The fact that objects struck by lightning were often buried in the ground means they were often unusually well preserved for future archaeologists. This was the case for the discovery of the largest gilded bronze statue that currently survives from the Roman world, the Hercules Mastai Righetti. The 13-foot-tall demigod statue, which dates to between the first and third centuries A.D. and sits in the Vatican Museums today, emerged from the ground during work on a villa near Rome’s Campo dei Fiori in 1864, much to the shock of the workers. Nearby, a small slab made of travertine marble bore an inscription that read F.C.S, an acronym for fulgur conditum Summanium. Hercules had been struck at night, just like the objects buried at Hadrian’s Villa.

In addition to patchwork of archaeological evidence for the practice, Roman literature tells us much of what we know about reactions to the ancient bolts that struck Roman buildings, statues, or even temples. The ancient biographer Suetonius noted that Emperor Augustus erected the Temple of Apollo within his residence on the Palatine hill in Rome after it was struck by lightning and the priests interpreted this as Apollo claiming the space for himself.

And in his treatise on religious divination called De Divinatione, Marcus Tullius Cicero recorded a moralizing anecdote about the time a lightning bolt struck the Temple of Jupiter Optimus Maximus in Rome amid a time of uncertainty during the emerging empire’s war with Greek King Pyrrhus of Epirus in 278 B.C. Cicero was himself a member of Rome’s sacred college of augurs, who interpreted the sky for divine signs. The orator recounted how the terracotta statue of Summanus on top of the temple was struck. When its head could not be found, the haruspices asserted that it was thrown into the Tiber. And indeed the head was found within the river exactly where they had predicted. “Is it possible for us to doubt the prophetic value of lightning?” Cicero exclaimed. The priests interpreted the lightning strike as Summanus desiring his own temple, so the Romans quickly built a temple to the nocturnal god on the slope of the Aventine near the chariot track called the Circus Maximus. To the Romans, there was little doubt that lightning strikes required action.

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The new inscription at Hadrian’s Villa is not simply a slab steeped in the superstition of a bygone religion. The find adds to our knowledge of Roman religious ritual and the creation of sacred spaces, and it speaks to the everyday religious beliefs and practices at play within the Hadrian’s Villa. This is important for historians as they recreate the daily lives and religious beliefs of the two or three hundred administrators, craftspeople, and servants that modern archaeologists estimate lived on the estate. Smaller shrines to Summanus or the household gods called the Lares all existed alongside much larger ritual spaces, such as the villa’s temple dedicated to the Greco-Egyptian god Serapis, the Serapeum.

Like the city of Rome, Hadrian’s Villa had a complex religious topography that physically reflected the religious beliefs of its inhabitants—not just the will of the emperor Hadrian. Extreme weather and the divine omens of the past are long gone, but the impact that these events had on ancient Romans and their cities echoes in the inscriptions, shrines, and buried objects still emerging from the soil.