More than a million people a day are expected to be traveling between Europe and Asia in an underwater railway tunnel in Istanbul, Turkey. The total commute time between the two continents is scheduled to take about four minutes.

The $4.5 billion Marmaray tunnel runs 180 feet below sea level, officially connecting Europe and Asia, with the Bosphorus water way running just above it. Launched in 2004, the Marmaray rail has finally reached completion, with its opening coinciding with the 90th anniversary of the Republic of Turkey.

With a population of nearly 16 million people, two Istanbul bridges already accommodate nearly 2 million commuters a day, according to Agence France-Presse. Turkish officials hope the railway will relieve some of the excess traffic that Istanbul is known for.

"While creating a transport axis between the east and west points of the city, I believe it will soothe the problem" of congestion, Istanbul's Mayor Kadir Topbas told BBC.

The Turkish government expects the 8.5 mile long tunnel to establish an important trade route BBC's James Reynolds reports. Ultimately, the linkage symbolizes a future where one will be able to travel from London to Beijing through Istanbul, by train.

In the course of creating this "modern Silk Road" that will seamlessly connect Turkey to China, workers discovered artifacts dating back as far back as 6400 B.C.. A 4th century Byzantine port was among the most significant archeological discoveries found beneath the shores of the historical metropolis. But these discoveries also posed unexpected interruptions for construction on the railway.

The tunnel has also gone through a special construction process that will allow it withstand earthquakes. Due to Turkey's positioning along a major fault line, and it's past history of massive earthquakes, transport minister Binali Yildrim made sure certain building precautions were followed giving Marmaray the ability to withstand a 9.0 magnitude earthquake.

As with most great accomplishments, this tunnel was not built without opposition. CNN reports that Turkey Prime Minister Recep Tayyip Erdogan, one of the primary champions of the project, was accused of using the tunnel as a grandiose promotion to build his legacy. He has a number of other extravagant construction proposals that he hopes to fulfill including a third airport and a third bridge above the Bosphorus River.

But Erdogan claims these monumental construction projects will ultimately assist Turkey in becoming one of the dominant economies of the world by doubling its gross domestic product to $2 trillion.