Laser Scanning the Underworld of Rome

Mile after mile of Catacombs get documented in 3D for first time

by Justin Barton
May 5, 2009
Below Rome, Italy, burrowed into the soft yet durable volcanic tufa rock, are over 170km (105 miles) of winding catacombs. There are over 40 individual catacombs, dating back two millennia, which were carved out as protected burial sites for the religiously persecuted--the Christians, Jews, and Pagans--during a span of over three centuries. The largest catacomb is Saint Domitilla, which resides just outside Rome. It is 2000 years old, and extends 15km (9mi) through multi-level tunnels, caves, galleries and burial chambers.

These tunneled tombs beneath Rome are almost entirely inaccessible to the public due to safety concerns and currently only 0.5km (1640 ft) of the 170km are publicly accessible. The tunnels have also only ever been mapped by hand. And so three years ago, Dr. Norbert Zimmerman of the Vienna Academy of Science, decided to accurately map these ancient underground monuments by implementing state-of-the-art technology: terrestrial 3D laser scanners. For the last three years, Dr. Zimmerman and a team of 10 Austrian and Italian archaeologists, architects, and computer scientists have used a laser scanner and externally mounted digital SLR cameras to collect accurate, photo-realistic, 3D data of Saint Domitilla. In total, 4 billion data points were collected by the scanner.

The team has plans to eventually grant public access to some of the data, allowing for 3D, virtual access to previously inaccessible catacombs, including visualizations of paintings on the walls that have not been seen in 2000 years. Dr. Zimmerman says of the data, "It is not a virtual image, it is not an animation -- what you are seeing is real data ... [which] gives you the chance to compare areas, to assess the ways the catacombs were developed over time, to analyze how and why those who built them did what they did. That's never been possible before." The team will spend another year analyzing the data from the project. At the moment there are no plans to digitally record and preserve the remaining 161km (96mi) of catacombs. However, Zimmerman adds that scanning all of the underground works is necessary if we are to one day "really understand this incredible historical phenomenon and if we are to make a proper detailed study whilst these caves are still intact."
Scanning the catacombs (photo from
Laser scan data of the Saint Domitilla catacombs (image from
Point clouds and photo-textured point clouds of the catacombs (image from