The project to extend Rome’s Metro Line C under ancient Roman ruins and through Rome’s historic centre has advanced to a crucial stage. Engineers have started the construction of an 85-metre deep retaining wall surrounding the main station at Piazza Venezia.
During a site tour on Thursday, chief engineer Andrea Sciotti gave details on the nearly €3billion project recognised as one of the most challenging worldwide. The completion date is another ten years hence, in 2034.
The Metro C subway line has been in the pipeline for twenty years but has faced numerous setbacks due to bureaucratic hurdles, funding issues, and the extensive archaeological excavations required to navigate the ruins of Imperial Roman and Medieval civilisations beneath Rome.
Once finished, the Metro C line will pass under some of the world’s most important cultural heritage sites, including the Colosseum, Trajan’s Column, and the Basilica of Maxentius, the largest building in the Roman Forum. It will also tunnel beneath notable Renaissance palazzi, churches, and the Vatican.
Given the historical and cultural significance of the route, Italy’s culture ministry has been actively involved throughout the process. As excavation begins on the first 15 metres of the Piazza Venezia station, where ancient Roman ruins lie, archaeologists will oversee the digging. They will ensure the preservation of artefacts for study, restoration, and future display in a museum within the station.
“I think I can say it’s unique in the world because we don’t only have the Colosseum and the Basilica of Maxentius, but we have 15-20 metres of hidden archaeological patrimony – known but hidden,” Sciotti told reporters. “This obviously brings problems that must be resolved in the planning and realisation phases.”
10 years to complete Metro C extension
To underscore the complexity of constructing the Piazza Venezia hub, Sciotti pointed out that while it will take 10 years and €755 million to complete this station. Four other stations along the Metro C line, extending beyond the Vatican, will also be constructed during this period.
“Twenty, thirty years ago, it would have been very difficult to do this,” he said. However, advancements in technology now enable excavation beneath archaeological sites while safeguarding the above-ground heritage. Sciotti has even shared the Metro C project with engineers in Ecuador, who are planning a similar subway line through Quito’s historic centre.
Currently, the project focuses on the preliminary phase of constructing the 85-metre deep retaining wall of reinforced cement around the Piazza Venezia station. This involves using a hydro mill trench cutter to dig rectangular-shaped columns that are then filled to form a watertight retaining wall. This will secure the site’s perimeter before the actual excavation starts.
Although central Rome already has two main subway lines, including one with a stop at the Colosseum, the Metro C line will penetrate the heart of the historic centre and connect it to the Vatican and beyond. It will offer much-needed improvements to Rome’s public transport system.
Currently, Line C runs from the Rome suburb of Montecompatri/Pantano and stops at S.Giovanni.
Need to minimise vibrations
Once the line reaches Piazza Venezia, the tunnels will run at a depth of 45 metres underground, minimising vibrations that could affect the historic palazzi and churches above.
When completed, the eight-level Piazza Venezia station will provide underground links to the Vittoriano “wedding cake” monument, the Palazzo Venezia museum, and the museum under Hadrian’s Athenaeum, constructed in 123 A.D.
Sciotti expressed particular concern about the work near the Hadrian archaeological site, where the delicate Trajan’s Column stands. Despite meticulous monitoring and the use of buffering techniques to limit vibrations, similar to those used on London’s Jubilee tube line, he remains apprehensive.
“If anything happens to the Trajan’s Column, I have my passport ready,” he joked.
Line C project facts
We Build Group, who are responsible for the construction of Line C, state on their fact sheet that the line “unites the past and future of Rome”.
In total there will be 29 stations, of which 3 are under construction, 22 are active and 4 are in the planning stages.
There will also be:
- 29 archaeological sites
- 4 museum stations
- 800,000 passengers per day (24,000 per hour in each direction)
- More than 500,000 artefacts found
- 98,000 m2 of ‘green’ areas
- 1st automated and driverless line in Rome
