The ancient mystery cults that Greeks and Romans followed in the privacy of their plush homes or the shadows of dank caves are being illuminated at the Colosseum in an impressive light-and-sound show. More than 70 works including statues, frescoes, ritualistic objects and private altars bear testimony to the increasing popularity of Dionysan, Eleusine, oracular, Orphic and Mithraic rites as adepts reached for meaning and salvation outside organised religion .

A series of marble heads from Calabria illustrate the Eleusine mysteries, related to fertility .

Adepts were devoted to two goddesses, Demeter the grain goddess, and her daughter Persephone, also known as Kore (the Maiden). Demeter gave the Greek city of Eleusis two things: grain as the basis of civilisation and the mysteries which held the hopes of a happy afterlife. The exhibition contains an array of representations of the massively popular god of wine, ecstasy and fertility, Dionysus .

Bacchanalian orgies devoted to the god are perhaps the most famous examples of secret rites. They were suppressed by the Roman senate in 186 BC .

Sculpted maenads - frenzied women who tore the god to pieces - are a highlight of the show. They are linked with bas reliefs depicting the related Orphic mystery, which stems from the legend of Orpheus who tragically turns back to see if his wife Eurydice is following him from the Underworld and thus consigns her there forever. The exhibition also contains several statues of the eastern deities Romans embraced from the 2nd century AD: Cymbele the earth goddess, the Egyptian divinities Isis and Osiris, and the Persian god Mithras .

Unlike other rites such as Christianity, these were increasingly tolerated as a form of political control over the Roman people .

Some believe Mithras - and also Dionysus - made it easier for Romans to eventually accept Christianity .

As early as their so-called archaic age, the Greeks had 'borrowed' Isis and Osiris, identifying them with Demeter and Dionysus .

Osiris married his sister Isis, who like him symbolised the passage of time and entry into the afterlife. Many Roman sanctuaries with Egyptian gods and 'Egyptianising' priests were later established, particularly the temple of Isis at Rome under Caligula. Mithras - whose famous depiction as he slays a mythically powerful bull is one of the other stand-out statues on view - was an ancient Indo-Iranian deity, found from the Bronze Age onward. The cult, which was brought back from the East by Roman legionaries, held its initiations in caves and had sacrificial meals there .

The exhibition concludes with a series of Mithraic objects that demonstrate how later Roman rites tended towards monotheism .

The Secret Rite: Mysteries in Greek and Rome has just opened and runs until January 8