Pioneering Laser-scan Technology Brings Rome's Catacombs to Life

A group of international archaeologists and scientists have completed the first phase of a massive project to laser-scan Rome's Domitilla Catacombs, and are currently analysing their data. The project, which has so far lasted three years, intends to capture a three dimensional image of the catacombs' huge network of underground chambers.

The process is based on a sophisticated laser scan technique, which creates a 3D 'point cloud' of the interior of each section of the catacomb from recorded coordinates. This is then digitally combined with photos taken from a camera attached to the scanner, achieving a 3D photographic model based on real and accurate data, which can be explored and studied in several different ways.

Down and Out in Rome

The Domitilla Catacombs date back to the second century AD and lie about two kilometres to the south of Rome's city centre, near the via Appia Antica. They are one of 40 underground burial chambers in the city – the most-visited are the nearby catacombs of San Sebastiano and San Callisto, the latter of which has almost 20 kilometres of underground tunnels.

Domitilla is the oldest and is also the only one of Rome's catacombs that still contains some human remains. It  has an extensive network of tunnels and caves covering about 15 kilometres. Most importantly of all, many of the burial chambers are decorated with a series of important and unique wall paintings and other decorative elements, providing valuable insight into early Christian, Jewish and pagan artwork. Many of the frescoes at the Domitilla Catacombs haven't been studied in depth, mainly because access is difficult and data about the site and reproductions of the frescoes are all too scarce.

One Giant Leap for Laser-scanning

This situation is set to change, with a huge amount of data already recorded. According to project leader Dr Norbert Zimmerman, archaeologist at the Austrian Academy of Sciences' Institute for Studies of Ancient Culture in Vienna, the laser scanner took two billion points of reference during 2,000 separate scans inside the catacombs.

It is important to stress that the digital model of the Domitilla Catacombs differs significantly to the many 'virtual reality' models and recreations of ancient cities, sites and monuments that are available on the Internet (such as Google Earth's virtual ancient Rome, Acropolis and ancient London as well as the UCLA's Qumran). It is, in technological terms, an evolutionary step ahead of these.

The level of accuracy and detail achieved by the 'point clouds' is incredible, with the overall effect coming across as more like a film than a digital reconstruction - but a film where you can move around and view the catacombs from different angles.

Going Underground: Cramped Working Conditions

Zimmerman describes some of the difficulty which he and his team encountered during the scanning project inside the Domitilla Catacombs, which are closed to the public due to the unstable environment and danger of damage to the tomb paintings. He says: “There were difficulties for the scanner because we needed to light the underground chambers in order to take the photos, but with 15 kilometres of dark tunnels, getting adequate lighting down there wasn't easy.”

Some of the project's most exciting moments happened in the depths of the catacombs. Zimmerman says: “Of course the most exciting part of my job is when you feel like you have seen something new and there were several moments like that at the Domitilla Catacombs, for example when we found some 200-year-old sketches inside the caves of the tomb paintings. But perhaps the most exciting part of this project has been in the post-production process, seeing the data we gathered inside the catacombs taking shape on screen into a 3D model that we can fly through using a joystick. The model can be viewed from any angle and it can tell us a lot about the topographical development of the catacombs. That for me is one of the most interesting things.”

The combination of dimensional and visual data enables scientists and archaeologists to study the way in which this unique site took shape over three centuries, developing from separate pagan and group burial chambers, into a large connected network. When the site became disused as a necropolis after the fifth century, a basilica was built at the centre of the network of burial chambers. Containing the graves of the martyrs Nereus and Achilleus, it was a centre for pilgrimage until it too was abandoned after the ninth century.

Unique Discoveries of Early Christian Art

So why the Catacombs of Domitilla? Apart from being Rome's oldest and biggest underground necropolis, these particular catacombs, sculpted out of soft tufo rock, are extremely well preserved. The digital image of the catacombs will provide valuable material for historians of early Christian art. The works range from early pagan and Christian paintings from the second century AD, up to the more developed and stylised Christian iconography associated with the era of Constantine I during the fourth century. One of the second century frescos in the Domitilla Catacombs depicts a scene from the last supper and there are many other important early Christian artworks inside the catacombs network. The digital imaging of these catacombs is a vital part of the process of studying this early religious art and will provide archaeologists and historians with new and unique primary material to further our understanding of religion, art and burial during the Roman empire. 

The work is important because much is still not known about the site, despite past excavation and research. Many parts of it have still not been examined in any detail – and according to the Institute for Studies of Ancient Culture at the Austrian Academy of Sciences, this is partly because the catacomb has not been considered in its entirety as a single archaeological site. Despite the fact that the catacomb is in good condition, until now there has been surprisingly little data about the dimensions, contents and history of the site.

The most interesting discoveries so far are:

• a painting of Nereus and Achilleus – the two Saints also associated with the site along with Saint Domitilla (whose real name was Flavia Domiciliary, a descendent of the emperor Vespasiano and now a saint in the Greek Orthodox Church).
• a scene from the legend of Saint Thecla, an early Christian saint who is said to have been a follower of St Paul and was renowned for defending her virginity.
• an image of the grave-digger (or fossor) Diogenes.

In fact the Domitilla catacomb contains more than 80 painted tombs and there is huge potential for further study. Gathering scientific data, including images, dimensions and topographic development, will be a vital part of the analysis and understanding of the site's history.

Bringing Domitilla to the Public?

Zimmerman's team are currently producing a repertory of the the catacomb's paintings which will provide valuable study material for ancient art historians. While the project's aims are primarily academic, to further the archaeological and historical understanding of the catacombs, Zimmerman does not rule out that the digital model may one day be available to the public – either online, on dvd, or through a museum installation, which would allow the public to explore the catacombs. With the actual catacombs currently closed to the public, we hope that the digital version will be opened soon.

Photos courtesy of Dr N Zimmerman from the Austrian Academy of Sciences and the Technical University of Vienna.

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Bija Knowles

Last three pieces by this author:

5 Interesting Facts to Impress Your Fellow St Patrick's Day Drinkers | New Exhibition: How Greek Culture in the Age of Conquest Changed Roman Art | Brittania Superior 'v' Brittania Inferior: the Roman Roots of Britain's North-South Divide

Bija Knowles is a freelance journalist based outside Rome, Italy. She graduated in Italian and English Literature from the University of Birmingham, UK, and her main areas of interest are art, travel and history in Italy.