大成建設
Plans to build a modern trans-Bosporus tunnel were proposed in 1997, based on a feasibility study ten years prior, and the necessary capital secured in 1999. Preparatory works on the project began in 2001. Construction began in May 2004. The tunnel was constructed by a Turkish-Japanese consortium led by the Taisei Corporation. Tunnel construction was completed on 20 October 2008, and rails were added in 2009. The completion of the project was delayed due to archeological discoveries near Sirkeci, with artifacts dating back 8,000 years.