October 29 marked the 90th anniversary of the formation of the Turkish Republic, and residents of Istanbul had an extra reason to celebrate. The date marked the opening of the first phase of the Marmaray project, a large regional rail effort that includes an undersea tunnel that now allows commuters to take a train across the Bosphorus Strait and skip Istanbul's notoriously congested roadways.

The newly opened section extends underground for 8.5 miles (13.6 kilometers), with 0.8 miles (1.4 kilometers) buried under the seabed, nearly 200 feet (56 meters) under the water of the strait.

When designing the tunnel, engineers had to take into account its proximity to the active North Anatolian Fault, which lies about 10 miles (16 kilometers) away.