File talk:Tünel-Istanbul2.JPG

Little more than cable car on rails
To describe this as an underground metro is pushing the limits. in 1830, Liverpool had a tunnel, the Crown St tunnel, with open air stations each end. As it was on an incline, the trains were pulled by cable - the locos took over on the level. This is very similar, except the open air stations and less of an incline in the tunnel. Looking it it, I can't why it wasn't built on the side of the hill rather than in an expensive tunnel.