Priceless Naples treasure of San Gennaro goes on show Published duration 30 October 2013

media caption As David Willey reports, the jewels have rarely left their strongroom

One of the world's most valuable collections of jewels, dedicated to the patron saint of Naples, has gone on show in an unprecedented exhibition.

The treasure of San Gennaro is said to rival Britain's Crown Jewels and those of the Russian tsars in value.

The 70 pieces were transported under armed guard to a museum in Rome.

They include a bishop's mitre encrusted in stones, and a large necklace composed of thousands of gems, donated by many crowned heads of Europe.

The jewels, statues and religious items such as golden chalices were donated over several centuries to the patron saint of Naples, San Gennaro, or Januarius in English.

But for much of that time, the treasure of San Gennaro was kept away from the public eye in a vault in Naples cathedral.

Gennaro, the bishop of Naples, was martyred in the third century.

He has been venerated down the centuries as the city's protector against war, the plague, earthquakes, shipwrecks and natural disasters, says the BBC's Rome correspondent, David Willey.

In the 1520s, when Naples was beset by disease, war and the frequent eruption of the nearby Mount Vesuvius, Neapolitans pledged to build a chapel to San Gennaro and safeguard the donated treasure, in return for the saint's protection.

image caption The Mitre of San Gennaro is one of the highlights of the exhibition

image caption A bust of Saint Januarius, or San Gennaro, who is considered the saint protector of Naples

image caption In times of strife, Neapolitans pledged to build a chapel to San Gennaro in return for his protection

image caption Some experts consider the collection more valuable than that of the former czars of Russia

image caption The Mitre of San Gennaro was commissioned to crown a bust of the saint carried in religious processions

"The city was on its last legs, but the people of Naples knew which saint to turn to, " said the exhibition's curator Paolo Jorio.

"They voted that, if Saint Januarius helped them, they would dedicate a new treasure chapel to him."

Pope 'not expected'

"They commissioned, set up, safeguarded and managed all the masterpieces that from 1305 until today have been given to the chapel, building a patrimony of 21,610 masterpieces," he said.

Kings, popes and emperors have all sent valuable tributes to the saint's shrine.

Emmanuele Emanuele, head of the Rome Foundation organising the exhibition, told reporters the collection was "of incalculable worth, both historically and artistically, greater than that of the British Crown Jewels or the Russian imperial crown".

One of the highlights of the exhibition is a bishop's mitre, decorated with 3,964 diamonds, rubies and emeralds, commissioned to crown a bust of the saint carried in procession in Naples on his annual feast day.

But perhaps the centrepiece of the exhibition is the necklace of San Gennaro, which was begun in 1679.

Considered one of the most exquisite items of jewellery in the world, it has been forged from several ornate pieces, including a jewel-studded cross donated by the French emperor Napoleon Bonaparte.