You are looking at the 2nd oldest subway system in the world. The Tünel was built back in 1875 by French engineer Eugène-Henri Gavand. It connects the major Istanbul neighborhoods of Karaköy and Beyoğlu, which are separated by a steep hill with very narrow streets. A single track splits off in the middle, allowing the 2 subway cars to pass each other. The $2 ride only takes one and a half minutes.