Over two thousand years, it has been stripped and dismantled for building materials, stone, marble, and travertine. It has endured earthquakes, traffic, and concerts. And yet, the Colosseum, Rome’s symbol, remains remarkably sound.
“Especially from satellite data, which show us long-term results, we have seen that the Colosseum is very stable,” explains Andrea Schiappelli, archaeologist at the Colosseum Archaeological Park. “One of its strengths is its ring-shaped foundation made of concrete, a mix of cement mortar, basalt and tuff fragments, and likely even rubble from Nero’s Domus Aurea, which the Flavians demolished to make space for the amphitheater and other buildings.”
Pomerium, e-GEOS and ESA for Ancient Rome
To monitor some of the most important monuments in the heart of the capital, the Pomerium project was launched. Conducted by e-GEOS with a consortium of companies and research institutes on behalf of the European Space Agency (ESA), it focused on the Colosseum, the Pyramid of Cestius, parts of the Aurelian Walls, the Baths of Caracalla, and a section of the Tiber River that includes historic bridges.
“Pomerium is a project dedicated to monitoring the stresses these monuments suffer in an urban environment, and therefore to their prevention and proper maintenance,” explains Manuela Ferri, Project Manager at e-GEOS. “We mainly analyzed ground stability risk using interferometric techniques based on radar satellite data, which can detect even millimetric or sub-millimetric ground movements.”
Pollution, vibrations caused by concerts or construction work - such as metro lines- as well as the constant flow of trams and heavy vehicles, subject the monuments to continuous stress and slow, inevitable deterioration.
“This must absolutely be monitored to prevent and stop it as soon as risk thresholds are reached,” adds Schiappelli.
“It’s not just the constant flow of millions of tourists every year,” continues Ferri. “Smog is also extremely dangerous because certain pollutants chemically alter materials, making them more vulnerable to rain, wind, and erosion. As the material becomes more porous, it’s more easily attacked by mold, bacteria, and moss.”
Data collected from air-quality sensors, processed using artificial intelligence models, have produced forecasts of the deterioration rate of building surfaces exposed to urban environments, particularly the travertine of the Colosseum and the marble of the Pyramid of Cestius.
The park’s control center
“Our general monitoring strategy here at the park is to centralize all information on a single platform,” says Schiappelli. “We use sensors such as velocimeters, accelerometers, and sound level meters to measure noise, like that from concerts at the Circus Maximus. This way, we can have a central control room that sends alerts to officials responsible for restoration and maintenance, preventing risk thresholds from being exceeded.” Satellite data, such as radar data from the Italian COSMO-SkyMed constellation and the European Copernicus Sentinels measure variations in the elevation of monuments, showing whether they are subsiding or rising due to long-term phenomena like earthquakes or ground movements.
Climate, weather, and cultural heritage
Monuments and cultural heritage sites are also threatened by climate change–related phenomena, such as extreme weather events, torrential rains, and floods that cause rivers to swell rapidly.
“Regarding the Tiber River, which runs through the historic city, we monitored the presence of debris floating in the water,” explains Ferri. “Large accumulations can obstruct bridge arches and, in the case of historic bridges such as Ponte Milvio, may even cause partial or total collapses.”
e-GEOS employs advanced technologies such as digital twins to model and analyze sites of interest. “Digital Twins are the ultimate tool because they allow data to be visualized in a context that faithfully reproduces reality and show predictions generated by AI-based models,” Ferri continues. “This makes it immediately clear what could happen in an urban area under certain scenarios.”
“We tested and refined this approach in the monitoring project of the Sibari archaeological site, which is particularly exposed to flood risk. We succeeded in developing a predictive tool that enables park management to mitigate damage from potential events, knowing in advance their possible extent and severity.”