By Melanie Lieberman
October 30, 2013

Turkey opened its new tunnel connecting Europe and Asia yesterday. For the first time, travelers can cross the Bosporus Strait (and continents) in roughly four minutes, via the world’s deepest sub-sea tunnel.

This underwater tunnel between the European and Asian shores of Istanbul is the realization of a Sultan’s dream 150 years ago. Now, on the 90th anniversary of Turkey’s independence, it is truly united.

Prime Minister Tayyip Erdogan inaugurated The Marmaray Rail yesterday, after nearly 10 years and $2.8 billion dollars. The project is far from over, however. The tunnel is only a quarter of what Erdogan calls “a project for whole humanity.”

As this historic metropolis transforms into a global superpower, plans for a new suspension bridge across the Strait, a third airport, and a massive canal that would bisect Istanbul and leave half the city as an island are already underway.

Until then, this free-standing tunnel, submerged more than 180 feet below the surface, is a record-breaking feat that, even alone, adds to Turkey’s ancient legacy of innovation.

While helping untangle the snarl of commuters crossing the continents twice a day—as many as 2 million—the Marmaray link also uncovered 40,000 artifacts, including 35 Byzantine shipwrecks. These discoveries helped archaeologists map Istanbul’s history back more than 2,500 years than earlier than imagined.

Melanie Lieberman is an editorial intern at Travel + Leisure.