World’s deepest submerged tunnel to connect Asia and Europe

Istanbul has been at the economic focal point between Asia and the West for a long time. Running almost 200 feet below the surface of that narrow channel of water, the 8.5-mile long railway now holds the claim to “the world’s deepest submerged tunnel.” Istanbul city officials hope the Marmaray tunnel, capable of transporting up to 1.5 million passengers a day, will help ease the flow of traffic from the two existing bridges on either side of the city. Another future hope is to make the tunnel a permanent part of the train route for rail travel between China and Western Europe. Running under the Bosporus strait, the 190-foot deep, 8.5 miles long tunnel was unveiled on the 90th anniversary of the Turkish Republic, after eight years of construction.

The project was beset by long delays owing to archaeological excavations: the remains of a Byzantine shipping fleet, the largest discovered, were found at the main metro terminus in Yenikapi, prompting Erdogan to voice contempt that construction was held up because of “clay pots” and “other stuff”. The tunnel is the world’s first to connect two continents: traveling under the waters of the Bosphorus strait as it joins the Asian and European halves of Turkey’s largest city together.

Japan Bank for International Cooperation invested $1bn of the $4bn (£3.4bn) cost of the project.

Once its safety is guaranteed would serve as an important step towards easing the notorious congestion in the city of 15 million people. Even amid these safety concerns, there’s no one arguing that this rapidly-expanding city doesn’t need more public transit options—the tunnel is expected to carry nearly a million commuters a day.