ABSTRACT: The construction of a sub-sea tunnel at Boğaz (Bosphorus) has been planned as a submerged funnel If thistunnel is constructed as a submerged tunnel it will be the deepest one in the world and it has many teehnologicall challenging problems. Besides environmental concerns, the adverse geotechnical conditions near Sirkeci onthe European side might present severe stability problems under both static and dynamic loading conditions,, Theauthor has presented an overall view of geology, geotechnical and environmental conditions and seismicity of theconstruction area,, Particularly, it is emphasized, out that the liquefaction of ground in the construction site during an earthquake greater than magnitude 6 may be a big concern for the tunnel It is pointed out that thepresently planned submerged tunnel is not suitable in view of its seismic stability, geotechnical conditions, constructional difficulties, environmental problems and disruptions of both national and- international sea traffics,.Furthermore, the suitability of shield tunnelling as an alternative is discussed ana* compared with that of the submerged tunnel If the sub-sea tunnel is constructed along the planned alignment, it will be better to locate the tunnel in ground, which is more resistant against liquefaction. Under such situation, the overburden of tunnel fromsea-bottom will be 2D or greater.. Since it is not possible to construct submerged, tunnels with such overburden,the shield tunnel should be the best option unless the route and the type of construction is changed...