Marmaray (pronounced [ˈmaɾmaˌɾaj]) is a partially operational rail transportation project in the Turkish city of Istanbul. It comprises an undersea rail tunnel under the Bosphorus strait, and the modernization of existing suburban railway lines along the Sea of Marmara from Halkalı on the European side to Gebze on the Asian side. The procurement of new rolling stock for suburban passenger traffic is also part of the project. Construction started in 2004, with an initial target opening date of April 2009. After multiple delays caused by the discovery of historical and archaeological finds, the first phase of the project opened on October 29, 2013. It is the first standard gauge rail connection between Europe and Asia.