VATICAN CITY - The Vatican unveiled the largest and most luxurious of the pagan tombs in the necropolis under St Peter's Basilica today, after nearly a year of restoration work.

The Valeri Mausoleum was built by a family of former slaves early in the second half of the second century, during the reign of Emperor Marcus Aurelius.

The new tomb, which is is one of 22 pagan tombs in the grottoes under the basilica, was shown to media today.

Tourists can have a guided tour of the grottoes by appointment.

The mausoleum is enclosed by glass and being monitored for temperature and humidity to help preserve it.

The once open-air pagan burial grounds were covered up by Emperor Constantine, a convert to Christianity, in the fourth century to build the first basilica over the site held as the tomb of St Peter.

The Valeri tomb, made up of several rooms and niches, is less than several dozen metres away from the burial place of the Apostle Peter, venerated by Catholics as the first pope.

Peter was martyred in Rome in the area near the Vatican known as Nero's Circus, during the first century persecution of Christians by the Romans.

"This restoration takes us straight to the font of the Catholic Church," said Cardinal Angelo Comastri, head of the Fabbrica di San Pietro, the office which for 500 years has been in charge of the running and upkeep of St Peter's Basilica.

The Valeri mausoleum was built by a family of former slaves who, once freed, amassed a vast fortune.

It is known as a particularly fine example of the stucco work popular at the time, for the bas reliefs and statues that adorned the mausoleum.

The tomb tells the history of the family, particularly in the bas reliefs of the head of a girl and a boy who were children in the Caius Valerius Herma family.

The children died young, possibly from plague.

Such stuccoed objects as a quill pen and a skein of yarn tell the tale of daily life in the Valeri family.

Reliefs of major gods and other pagan figures attest to their strong religious belief.

Several charcoal 'graffiti' of designs and Latin inscriptions were left untouched to allow for further research. Scholars think the inscriptions might indicate Peter's tomb.

In the guided tours, groups of 15 or fewer can see the grottoes. About 50,000 people visit the Vatican underground annually.

AP