Underground site to open to public twice a month.

Rome's Barberini Mithraeum, a mysterious cavern dating to the third century AD, is to reopen to visitors every second and fourth Saturday of the month, from 13 November.

Discovered by chance in 1936, the small archaeological jewel in the historic centre of Rome is located within the Palazzo Barberini complex, in the basement of the Palazzina Savorgnan di Brazzà.

The mithraeum, which measures about 12 x 6 metres, is one of the best preserved of its kind in Rome and has long been inaccessible to the general public.

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The rectangular chamber has a vaulted ceiling and a striking fresco depicting the god Mithras sacrificing the bull, with ten pinakes, or votive boards, shedding light on the Mithraic mysteries.

Mithraism was a Roman mystery religion centred on the god Mithras, the Iranian god of the sun, justice and war in pre-Zoroastrian Iran.

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Known as Mithras in the Roman empire during the second and third centuries AD, this deity was honoured as the patron of loyalty to the emperor.

Mithraism declined rapidly after the acceptance of Christianity by Emperor Constantine in the early fourth century.

For information on the site see Rome's Superintendency website and for reservations see the Coopculture website.