A faded painting, still showing hints of its once-vivid hues, fills the entire back wall of an otherwise grim underground cavern in Santa Maria Capua Vetere, Italy. Sculptures and frescoes of ancient gods and cryptic celestial symbols are scattered throughout the interior. A stagnant darkness lurks within the corridor, as the lack of windows forbids any stray sunlight to penetrate the ancient cave.
This subterranean temple is just one of more than 400 such structures that have been uncovered within the vast territory once overseen by the Roman Empire. It, like the others, is a relic from a mysterious ancient religion that continues to pose a challenge to most modern scholars.
Mithraism was an underground Roman religious group that worshipped a pagan deity called Mithras. All Mithraea featured a tauroctony, an image of the god Mithras slaying a sacred bull, as its centerpiece. Though the covert religion was once so widespread some historians considered it an early rival and “sister religion” to Christianity, little is actually known for certain about it.
The secretive cosmology of Mithraism has baffled people for nearly 2,000 years. Members of the cult-like religion don’t appear to have left behind any reputable written accounts of their inner workings, and if they did, the documents have joined the many other primary historical sources lost to time.
So scholars, spanning from ancient Greek and Roman writers up to modern-day academics, have been left to decode the mystery religion with the clues they’ve uncovered within the Mithraea, their underground temples. As David Ulansey writes in his book The Origins of the Mithraic Mysteries: Cosmology and Salvatio in the Ancient World, the unexplained artwork “constitutes one of the great unsolved puzzles of classical and religious scholarship.”
But Ulasney thinks he may have solved the puzzle. According to his theory, the cult’s central iconography is a star map. The bull Mithras kills in the tauroctony is actually the zodiac Taurus. By slaying Taurus, the god is therefore responsible for shifting the precession of the equinoxes. This cosmic movement was secret knowledge shared among indoctrinated members of the ancient cult during a time when the universe was still seen as a stagnant entity.
His hypothesis is one of the few relatively recent attempts to explain the core secrets of the mysterious cult. Even the namesake of the religion is shrouded in mystery. Ancient Romans believed Mithras was based on a Persian god, though most modern scholars have since debunked this theory.