The former Bosnian Eastern railway, between Sarajevo and Pale, has turned into a dirt track near the zone of Pale, a municipality in Bosnia and Herzegovina, located southeast of Bosnia's capital Sarajevo. This gravel track includes 99 tunnels and several bridges, some of them really dangerous. The builders could have easily blasted the rock and made it a stonecut instead of a tunnel, but they chose to make a tunnel for a better engineering and artistic.
Tunnel #4 is curved to the left, so it is completely dark inside. Tunnel #5 is one of the darkest and scariest tunnels between Sarajevo and Pale. It is curved to the left and about 140 m long, so it is completely dark inside. The entrance of tunnel #5 is visible through tunnel #6. There is a completely rusted metal plate to the right of the entrance of tunnel #6, which used to show its designation and length. The distance between tunnels #6 and #7 is only about 10 meters, and the space between is a completely vertical cliff, so the road on that section is on a very tall retaining wall. Extreme terrain!
Tunnel #7 is probably the most vivid of all 99 tunnels of the former Eastern railway, as it was cut through a thin extruded rock, only around 10 meters before tunnel #6 (its entrance is visible behind tunnel #7). Tunnel #10 is 237 m long, so it is the second longest of all tunnels between Sarajevo and Pale (the longest is tunnel #8 - 240 m).Tunnel #11 is one of the most vivid tunnels between Sarajevo and Pale, because of the specific way it has been cut through the rock. It has no walls - it is a raw rock perforation! It is the last tunnel before entering Pale. Tunnel #12 has been utilized by the motorway since the 1980s. It was by far the longest tunnel of the former Eastern railway (it is 852 m long and has two alternating curves inside). It has a stone brick wall during its entire length. Today it is used for alternative unidirectional vehicular traffic. There is no artificial illumination inside the tunnel (not even the fluorescent wall signs!).
Pic: By Julian Nitzsche (Own work) [CC BY-SA 3.0 (https://creativecommons.org/licenses/by-sa/3.0)], via Wikimedia Commons