Rome's planned upgrade to its transport system hit a snag when ancient ruins were discovered right along the planned route, Italian media reported on Tuesday. Reactions to the discovery ranged from joy at discovering a new addition to the city's rich cultural heritage to consternation at what is likely to cause further stoppages for the already-delayed project.

"It's exceptional, not only for its good state of conservation but because it is part of a neighborhood which already included four barracks," said Rossella Rea, the city center's chief archaeologist, "and, therefore, we can characterize this area as a military neighborhood."

The Italian daily Corriere della Sera called the accompanying mosaics, frescoes and burial site with the remains of 12 ancient Romans "sensational," but questioned why authorities did not spot the anomaly when planning the extension to the city's underground train route.

Rea argued that it would have been "impossible" to spot the site before excavating.

This was the latest snag in plans to modernize and expand the C line, which began almost a decade ago. Corruption and funding shortages have seen work continue in fits and starts, with a new opening date scheduled for 2020. With a costs climbing beyond 4 billion euros ($4.5 billion), the Corriere della Sera estimated that it was Italy's most expensive public works project since World War II.

The city announced that it planned to incorporate the find into construction, without elaborating on how such a feat would be accomplished. Andrea Sciotti, an engineer involved in the project, told the press that the cost of doing so was an "unknown variable."