Archaeologists and art restorers using new laser technology have discovered what they believe are the oldest paintings of the faces of Jesus Christ's apostles.
The images in a branch of the catacombs of St. Tecla near St. Paul's Basilica, just outside the walls of ancient Rome, were painted at the end of the 4th century or the start of the 5th century.
Archaeologists believe these images may have been among those that most influenced later artists' depictions of the faces of Christ's most important early followers.
"These are the first images that we know of the faces of these four apostles," said Professor Fabrizio Bisconti, the head of archaeology for Rome's numerous catacombs, which are owned and maintained by the Vatican.
The frescoes were known but their details came to light during a restoration project that started two years ago and whose results were announced on Tuesday at a news conference.
The full-face icons include visages of St. Peter, St. Andrew, and St. John, who were among Jesus' original 12 apostles, and St. Paul, who became an apostle after Christ's death.
The paintings have the same characteristics as later images, such as St. Paul's rugged, wrinkled and elongated forehead and balding head and pointy beard, indicating they may have been the ones which set the standard.
The four circles, about 50 centimetres in diameter, are on the ceiling of the underground burial place of a noblewoman who is believed to have converted to Christianity at the end of the same century when the emperor Constantine made it legal.
Mr. Bisconti explained that older paintings of the apostles show them in a group, with smaller faces whose details are difficult to distinguish.
"This is a very important discovery in the history of the early Christian communities of Rome," said Mr. Bisconti.
The frescoes inside the tomb measuring about 2 metres by 2 metres were covered with a thick patina of powdery calcium carbonate caused by extreme humidity and no air circulation.
"We took our time to do extensive analysis before deciding what technique to use," said Barbara Mazzei, who headed the project. She explained how she used a laser as an "optical scalpel" to make the calcium carbonate fall off without damaging the paint.
"The laser created a sort of a mini explosion of steam when it interacted with the calcium carbonate to make it detach from the surface," she said.
The result was stunning clarity in the images that were before blurry and opaque.
The wrinkles on St. Paul's forehead, for example, are clear and the whiteness of St. Peter's beard has re-emerged.
"It was very, very emotional to discover this," said Ms. Mazzei.
Other scenes from the Bible, such as Jesus raising Lazarus from the dead or Abraham preparing to sacrifice his son Isaac, are now also much clearer and brighter.
"As far as paintings inside catacombs go, we are used to very faint paintings, usually white, with few colours. In the case of the St. Tecla catacombs, the great surprise was the extraordinary colours. The more we went forward, the more surprises we found," Ms. Mazzei said.
The tomb, in a web of catacombs under a modern building, is not yet open to the public because of continued work, difficult access and limited space. Mr. Bisconti said the new discoveries will be made available for viewing by specialists for the time being.