▁b ould ers ▁in ▁the ▁roof . ▁The ▁ca vers ▁removed ▁one ▁of ▁the ▁b ould ers ▁to ▁reve al ▁a ▁way ▁on , ▁which ▁led ▁via ▁a ▁dry ▁route ▁to ▁the ▁far ▁side ▁of ▁S ump ▁ 1 . ▁The ▁new ▁ ▁section ▁of ▁river ▁passage ▁beyond ▁was ▁named ▁Sk reen ▁Hill ▁ 2 , ▁and ▁a ▁further ▁ ▁in let ▁passage ▁was ▁named ▁Leg nab rock y ▁Way . ▁A ▁notable ▁feature ▁of ▁the ▁Leg nab rock y ▁Way ▁is ▁the ▁Gi ant ' s ▁Hall , ▁a ▁large ▁chamber ▁ 6 0   m ▁long , ▁ 3 0   m ▁high ▁and ▁ 1 5   m ▁wide ▁( 2 0 0 × 9 8 × 4 9   ft ). ▁Despite ▁only ▁carrying ▁a ▁small ▁stream , ▁the ▁Leg nab rock y ▁Way ▁is ▁the ▁largest ▁section ▁of ▁passage ▁in ▁Mar ble ▁Arch ▁C ave . ▁ ▁The ▁up stream ▁continu ation ▁of ▁the ▁river ▁in ▁Sk reen ▁Hill ▁ 2 ▁was ▁found ▁to ▁be ▁shortly ▁blocked ▁by ▁S ump ▁ 3 , ▁so ▁in ▁March ▁ 1 9 6 7 ▁a ▁team ▁of ▁divers ▁returned ▁to ▁attempt ▁further ▁expl oration . ▁William ▁F rak es ▁and ▁John ▁Og den ▁were ▁the ▁first ▁to ▁successfully ▁pass ▁the ▁ ▁sum p ▁to ▁reach ▁Sk reen ▁Hill ▁ 3 , ▁ ▁of ▁" m agn ific ent ▁stream ▁passage " ▁ending ▁in ▁b ould er ▁cho ke . ▁In ▁the ▁en su ing ▁months ▁a ▁compreh ensive ▁survey ▁was ▁made