When Paul was at Athens, he infamously made mention of “an altar with this inscription, ‘TO AN UNKNOWN GOD'” (Acts 17:23). A number of altars to “unknown” Greco-Roman deities have been discovered at Palmyra, an active trade hub in the Roman east (located in modern Syria). An example can be seen here. No such altar has yet been uncovered at Athens, but there is a contemporary example from ancient Rome.
This altar to an unknown god was discovered on Palatine Hill in Rome in the 1820’s. Palatine Hill was the location of the palaces of the Roman emperors, beginning with Augustus in the late 1st century BC. This particular altar has an inscription on its side that identifies it.
Altar to an unknown god, from Palatine Hill in Rome, late 2nd century BC.
The inscription is in Latin. Although somewhat weathered, it is still quite legible.
Front view of the inscription on the altar to an unknown god.
The inscription reads:
This may be translated, “Whether sacred to a god or goddess, Gaius Sextius Calvinus, son of Gaius, praetor, restored this on a vote of the senate.”
View of the back of the altar to an unknown god, Palatine Hill, Rome.
Amazingly, we also have a contemporary portrait of the man who left this inscription. Gaius Sextius Calvinus, is known to have been a praetor by at least 127 BC, and to have moved up to become a consul in 124 BC, providing a narrow window of time for this inscription to have been incised in the late 2nd century BC. This is his portrait, from the Fountain of Preachers, Aix-en-Provence, France.
Portrait of Caius Sextius Calvinus, who dedicated the altar to an unknown god on Palatine Hill in Rome; from the Fountain of Preachers, Aix-en-Provence, France.
Because the inscription attributes this altar to Calvinus, it is sometimes referred to as the Ara Calvini (“Altar of Calvinus”), although it is more commonly known as the Ara Dei Ignoti (“Altar of the Unknown God”).
Just briefly, how were such altars used? This Attic bell-krater shows a similar altar in use by a group of worshipers. The two figures at far left and far right hold sacrificial meat skewered on sticks.
This water jar shows three men roasting meat over an altar, a normal activity whenever a sacrifice was made in the Greco-Roman world.
Men roasting meat over a fire on a sacrificial altar, from Etruria, circa 530 BC.