Marmaray Tunnel, Railway tunnel beneath Bosporus strait in Istanbul, Turkey
Marmaray Tunnel is a railway passage running beneath the Bosporus strait, linking the European and Asian sides of Istanbul through a series of underground stations. The route uses electric trains that travel through two separate single-track tubes to carry passengers across the waterway.
Plans for bridging the Bosporus underwater emerged in the 1800s, yet construction did not begin until the early 2000s. The project finished in 2013, finally connecting the two continents by rail.
During construction, excavations near Sirkeci station uncovered pottery and tools from ancient times, revealing that people have moved across this strait for thousands of years. These discoveries show how this crossing has always been central to life in Istanbul.
Access is straightforward through stations on both the European and Asian sides, with short travel times requiring no special preparation. Since this is regular public transport, visitors should expect busier conditions during rush hours in the morning and evening.
The construction required engineers to lower massive steel tubes to the seafloor and sink them into place, a technique that had to be invented specifically for this project. This method set new records for underwater rail construction at the time it was completed.
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