of the valley, climbing 246 m level displacement to drainage divide Chukata and station Kostandovo ( 801 m AMSL) in 10.9 km. Here is the maximum slope of the route at 32 ‰. After passing this station, the route descends to Velingrad valley. In the beginning there are also stops Milevi skali at km 17.5 between Tsepina and Dolene and Dryanov dol between Dolene and Kostandovo. In the period of heavy traffic in 60s and 70s, Dryanov dol is extended with passing loop and becomes a station, but then it is completely closed, together with Milevi skali. Tsepina also had been station with passing loop and sidings, removed in 2003. All 10 tunnels on this part of the railway are between Marko Nikolov and Dolene. In April 1928 as a result of the Chirpan earthquake (M6.8), a huge amount of rocks collapses over the track at km 11.7. A new tunnel Nr 2 is constructed to avoid the small radius curves of the temporary track around the collapse. The abandoned old tunnel is still existing next to the new one. It is visible from the road, but not from the train. The open track between tunnels Nr 3, 4, 5, 6, 7, 8 is now covered to prevent another rock collapses on the route. Velingrad–Yakoruda This is the hardest section of Septemvri–Dobrinishte railway. It is 45 km long and all four spirals, 25 remaining tunnels and the highest railway station on the Balkans are here. Beginning from Velingrad, through Velingrad south stop, the line starts to climb along the right side of river Ablanitsa, heading Ostrets stop and station Cvetino. A few kilometers after Cvetino, the route turns to the right through the valley of the small river Lyuta reka, reaching the former station, now minor stop Sveta Petka. Here the route starts climbing 224 m in 9.8 km distance to station Avramovo, which is the highest railway station on the Balkans at 1267 m above sea level. Just after Tunnel Nr 16, the track passes a stone arch bridge over the river and begins its four-level way on the north side of the valley through 16 tunnels, two spirals and one 180° turn. The line passes under itself two times in tunnels Nr 18 and 24. In this section, the train changes its traveling direction 6 times. The average incline is 30 ‰. The climbing ends at station Avramovo