Istanbul is split between the historical and the modern, the secular and the religious, the tourists and the locals. But the most literal division of Istanbul is between two continents, Europe and Asia, which are separated by the Bosporus Strait. In the past, the only way to traverse this wide canal has been by bridge (traffic nightmares) or by ferry (pretty but slow). But now, finally, the two continental sides of Istanbul are being connected by the Marmaray tunnel, the world′s deepest immersed tube tunnel. The subway that will run through the Marmaray tunnel will not only be a bind together the city of Istanbul, but also connect Europe and Asia. Once the tunnel is completed, travellers will be able to ride from Portugal to China without setting foot off the train.