The Eurasia Tunnel consists of 3.4 miles (5.4 kilometers) of tunnel, about 2.1 miles (3.4 km) of that running directly under the Bosphorus. To avoid obstructing ship traffic, the tunnel was dug with a specially designed tunnel boring machine (TBM) from Herrenknecht through varying layers of rock and soft soil down to a depth of 347 feet (106 meters) below sea level.

The sheer size of the Eurasia Tunnel, more than 44 feet in diameter, did not make construction easy. But as of late 2016, about 100,000 vehicles a day have been crossing back and forth between the continents on two roadways one above the other.

A central view of the Herrenknecht Mixshield's cutting wheel, which was nearly as tall as a three-story house. To cope with the complex soil conditions, different excavation tools such as cutting knives and disc cutters were installed in the TBM.

The Eurasia Tunnel was a triumph of engineering. Never before had such a large-diameter tunnel been constructed under such high pressure with mechanized tunnelling technology.

Only 10.5 miles (17 kilometers) from the Eurasia Tunnel is a geological fault zone where earthquakes can have a particularly strong effect. In response to possible earthquake risks, special seismic joints were installed to give the tunnel flexibility.

The Eurasia Tunnel passes through a colorful patchwork quilt of soft ground, sandstone, mudstone, volcanic rock and solid rock, always under significant water pressure.