It is due to be operational by the end of 2017.

Story:CNNPictures: Reuters, AFP

longest-rail-tunnel (1)

longest-rail-tunnel (2)

longest-rail-tunnel (3)

longest-rail-tunnel (4)

longest-rail-tunnel (5)

longest-rail-tunnel (6)

longest-rail-tunnel (7)

longest-rail-tunnel (8)

longest-rail-tunnel (9)

longest-rail-tunnel (10)

longest-rail-tunnel (11)

longest-rail-tunnel (12)

longest-rail-tunnel (13)

longest-rail-tunnel (14)

longest-rail-tunnel (15)

longest-rail-tunnel (16)