▁c afé , ▁a ▁camera ▁obsc ura , ▁an ▁Ab original ▁museum , ▁a ▁" M other ' s ▁No ok " ▁where ▁visitors ▁could ▁write ▁letters , ▁and ▁a ▁" p ash ometer ". ▁The ▁main ▁att raction ▁was ▁the ▁view ing ▁platform , ▁where ▁" ch arm ing ▁attend ants " ▁assist ed ▁visitors ▁to ▁use ▁the ▁teles cop es ▁available , ▁and ▁a ▁co pper ▁cl adding ▁( st ill ▁present ) ▁over ▁the ▁gran ite ▁guard ▁rails ▁identified ▁the ▁sub ur bs ▁and ▁land marks ▁of ▁Sydney ▁at ▁the ▁time . ▁ ▁The ▁out break ▁of ▁World ▁War ▁II ▁in ▁ 1 9 3 9 ▁saw ▁tour ist ▁activities ▁on ▁the ▁bridge ▁ce ase , ▁as ▁the ▁military ▁took ▁over ▁the ▁four ▁p yl ons ▁and ▁modified ▁them ▁to ▁include ▁par ap ets ▁and ▁anti - air craft ▁guns . ▁ ▁In ▁ 1 9 4 8 , ▁Y v onne ▁R ent oul ▁opened ▁the ▁" All ▁Australian ▁Ex hib ition " ▁in ▁the ▁p yl on . ▁This ▁contained ▁di or am as , ▁and ▁displays ▁about ▁Australian ▁pers pect ives ▁on ▁subjects ▁such ▁as ▁far ming , ▁sport , ▁transport , ▁min ing , ▁and ▁the ▁armed ▁forces . ▁An ▁orientation ▁table ▁was ▁installed ▁at ▁the ▁view ing ▁platform , ▁along ▁with ▁a ▁wall ▁guide ▁and ▁bin oc ular s . ▁The ▁owner ▁kept ▁several ▁white ▁c ats ▁in ▁a ▁ro o ft op ▁c atter y , ▁which ▁also ▁served ▁as ▁an ▁att raction ,