- Marmaray tunnel project in Istanbul will be first railway connection between Europe and Asia
- The 76-kilometer route will ease commuter traffic on Istanbul's roads and strait
- Tunnel construction has been delayed by discovery of ancient artifacts
- Seismic activity also a consideration for contractors who have fitted "flexible joints" in the tunnel
As a city that sits astride two continents, Istanbul has always been a strategic gateway between the East and West. But an ambitious railway project is pulling the two continents even closer together with the construction of the world's deepest submerged tunnel.
The 76-kilometer (47.2-mile) Marmaray Project will include the world's first submerged railway connection between Europe and Asia, ferrying passengers under a 1.4-km (0.9-m) section of the Bosphorus Strait.
However, the massive infrastructure overhaul undertaken by Turkey's Ministry of Transportation has not been without problems. The project started in 2004 and has suffered multiple setbacks due to the region's rich heritage, as Turkey's transport minister Binali Yildirim explains.
"The tunnel is going under a very historical area, [a] historical peninsula where the Ottoman Empire settled ... so every piece of soil is examined by experts, archaeologists." Yildirim said.
At one point during construction, work had to be halted after the discovery of an ancient Byzantine port.
"If [the archaeologists] say you can go, we go. If they stay stop, we stop," Yildrim said.
All of which has added five years onto the original construction deadline.
To complicate matters further, the tunnel -- which passes under one of the busiest waterways in the world -- lies in an active earthquake zone.
"There is a big, huge seismic activity risk so we have seismic joints in the tunnels, especially between the immersed tube tunnel and the bore tunnel," says deputy project manager, Mehmet Cilingir.
The joints between the tunnels are flexible and will protect the structure from seismic movements, Cilingir says.
Despite the setbacks, the project is scheduled for completion next year -- a target that will be met, Yildirim says.
"We are very comfortable that the project is going to be complete by the end of next year. 14 million people are just waiting [for this tunnel to open."]
When it does, the tunnel is expected to ease the congested road and ferry routes above carrying 75,000 passengers per hour in each direction at peak times.
Train drivers, like Mustafa Berker, are already getting to grips with the new trains that will operate on the line.
"It will be a great joy for me if I too can add a bit to this big project," says Berker, a driver with almost four decades experience.
"I'm ready for my retirement but if I can see this through, it will be a great pleasure both for me, my children and grandchildren."