East meets West as Turkey connects the European and Asian part of Istanbul with a rail tunnel under the Bosphorus Strait, the busy shipping channel linking the Marmara and Black Seas

More than 14 million people and currently just two bridges in Turkey’s largest city mean chronic traffic congestion.

The earthquake-proofed twin tunnels are intended to partly address that problem.

Build by a Japanese-Turkish consortium they run for 13.6 kilometres of which 1.4 kilometres is under the Bosphorus itself.

The total cost was the equivalent of 3.3 billion euros and with trains running every two minutes at peak times it can carry 1.5 million people a day.

The shuttle service will connect with the wider Istanbul transportation network which is also being upgraded and extended.

It will be used by local passenger and freight services, with eventual plans for an international railway route between Europe and Asia.

This is the realisation of a dream going back over 100 years, but the tunnel’s completion was delayed for four years by the discovery of huge numbers of archaeological finds, some of which are now on display in, or portrayed on the walls of, the stations.