When Turkish rail workers began construction on a tunnel that would connect Europe and Asia and relieve traffic congestion in the heart of Istanbul in 2004, they hoped to finish the project by 2010.

What they didn’t count on was the discovery of the city’s largest Byzantine-era harbor, Port Theodosias, along the way. In addition to the fourth-century wall that most likely lined the city at the time of Constantine the Great, archaeologists have unearthed at least 34 ships and countless pots, skulls and other artifacts that suggest the area may have been settled as early as 6,000 B.C. (Archaeologists’ previous estimate had been 700 B.C.)

While the target dates for the tunnel’s completion have had to be pushed back to 2013, construction workers are taking delays in stride. “For this project we wait 100 years,” says a senior engineer at Marmarail. “So we can wait three years more, no problem.”