▁Council ▁on ▁Mon uments ▁and ▁S ites ▁stated ▁that ▁the ▁Haupt bahn hof ▁was ▁a ▁building ▁of ▁exception al ▁quality , ▁whose ▁integrity ▁should ▁be ▁maintained . ▁Since ▁ 2 0 0 9 ▁numerous ▁protest s ▁against ▁the ▁disput ed ▁project ▁have ▁taken ▁place . ▁On ▁ 3 0 ▁September ▁ 2 0 1 0 , ▁hundreds ▁of ▁demonstr ators ▁were ▁injured ▁when ▁the ▁police ▁used ▁water ▁can non , ▁pe pper ▁sp ray ▁and ▁bat ons ▁against ▁protest ors . ▁The ▁following ▁day , ▁more ▁than ▁ 5 0 , 0 0 0 ▁people ▁took ▁part ▁in ▁the ▁largest ▁demonstr ation ▁against ▁the ▁project ▁so ▁far . ▁ ▁Prior ▁to ▁that ▁es cal ation , ▁Frei ▁Otto , ▁one ▁of ▁the ▁architect s ▁responsible ▁for ▁the ▁project , ▁c ited ▁a ▁ 2 0 0 3 ▁report ▁for ▁calling ▁for ▁a ▁halt ▁to ▁the ▁project , ▁saying ▁the ▁ground ▁in ▁the ▁area ▁is ▁too ▁un stable ▁for ▁large ▁scale ▁under ground ▁works . ▁Some ▁critics ▁suggest ▁the ▁cost ▁of ▁the ▁project ▁might ▁rise ▁to ▁€ 1 8 . 7 ▁billion . ▁ ▁On ▁ 2 7 ▁November ▁ 2 0 1 1 , ▁a ▁refer endum ▁was ▁held ▁to ▁decide ▁whether ▁the ▁state ▁of ▁Baden - W ür ttemberg ▁should ▁ce ase ▁fund ing ▁for ▁the ▁project . ▁ 5 8 . 8 ▁percent ▁of ▁the ▁votes ▁cast ▁were ▁against ▁such ▁a ▁withdraw al . ▁While ▁some ▁consider ▁this ▁proof ▁that ▁a ▁majority ▁is ▁favour ▁of ▁the ▁project , ▁others ▁point ▁out