ruction ▁cam ps ▁were ▁established ▁in ▁Back n ang , ▁Mar bach ▁and ▁B iet ig heim ▁and ▁a ▁construction ▁headquarters ▁was ▁established ▁in ▁Mar bach . ▁The ▁entire ▁route ▁was ▁built ▁as ▁a ▁single - track ▁main ▁line , ▁but ▁the ▁line ▁was ▁prepared ▁for ▁event ual ▁dup lication . ▁ ▁During ▁the ▁construction ▁of ▁the ▁line ▁there ▁were ▁some ▁significant ▁problems : ▁c utt ings ▁of ▁up ▁to ▁ 1 3 ▁m ▁deep — the ▁deep est ▁in ▁Wür ttemberg — w ere ▁needed ▁through ▁gla cial ▁m ora ine ▁between ▁Bei hing en - He ut ings heim ▁and ▁B iet ig heim . ▁The ▁m ora ine ▁was ▁highly ▁s atur ated ▁and ▁was ▁subject ▁to ▁water ▁se ep age ▁and ▁land sl ides . ▁Three ▁f ount ains ▁were ▁built ▁to ▁dispose ▁of ▁the ▁water ▁and ▁were ▁used ▁to ▁supply ▁B iet ig heim ▁station . ▁Some ▁animal ▁remains ▁ab l ated ▁by ▁Ice ▁Age ▁gla ci ation ▁was ▁found ▁in ▁the ▁exc av ated ▁earth . ▁The ▁most ▁complex ▁structure ▁in ▁the ▁stretch ▁was ▁the ▁Ne ck ar ▁Vi ad uct ▁at ▁Mar bach , ▁which ▁was ▁built ▁as ▁a ▁five - span ▁steel ▁tr uss ▁bridge ▁with ▁a ▁total ▁length ▁of ▁ 3 4 5 ▁m . ▁ ▁Tra ins ▁began ▁running ▁on ▁the ▁Back n ang – B iet ig heim ▁line ▁on ▁ 8 ▁December ▁ 1 8 7 9 . ▁The ▁re building ▁of ▁B iet ig heim ▁station ▁made ▁it ▁the ▁second