The idea has been around for over a century, but has finally found fruition in 2013 (at least officially; it's far from complete). The project is called "Marmaray", getting its name from a portmanteau of a nearby water body and the local word for "rail".
What and where is this new international connection?
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This is a railway project that primarily consists of an undersea tunnel under the Strait of Bosphorus that links the European and Asian parts of Turkey.
More here.