▁to ▁the ▁public . ▁ ▁In ▁ 1 9 8 6 , ▁a ▁refer endum ▁was ▁held ▁which ▁designated ▁the ▁park ▁as ▁one ▁of ▁five ▁Natural ▁Heritage ▁Park s ▁in ▁the ▁area , ▁limit ing ▁the ▁amount ▁of ▁park ▁construction ▁and ▁development ▁to ▁five ▁percent ▁of ▁the ▁total ▁park ▁area . ▁ ▁Fe atures ▁ ▁Cl iff ▁C ave ▁ ▁Cl iff ▁C ave , ▁also ▁known ▁as ▁Indian ▁C ave , ▁is ▁a ▁natural ▁cave ▁that ▁is ▁considered ▁the ▁second ▁longest ▁cave ▁in ▁St . ▁Louis ▁County , ▁with ▁ 4 7 2 3 ▁ft ▁( 1 5 1 4 ▁m ) ▁of ▁cave ▁passage ▁survey ed . ▁It ▁is ▁found ▁at ▁the ▁head ▁of ▁a ▁rav ine , ▁with ▁a ▁stream ▁flow ing ▁from ▁the ▁entrance . ▁It ▁is ▁developed ▁in ▁Mississ ipp ian ▁Period ▁St . ▁Louis ▁lim estone . ▁The ▁cave ▁maintain s ▁a ▁temperature ▁of ▁ ▁all ▁year ▁round . ▁The ▁cave ▁was ▁created ▁from ▁the ▁kar st ▁plate au ▁in ▁the ▁area ▁forming ▁many ▁sink hol es , ▁dissol ving ▁the ▁dol om ite / lim estone ▁bed rock ▁over ▁time . ▁The ▁cave ▁is ▁connected ▁to ▁a ▁number ▁of ▁these ▁sink hol es , ▁causing ▁the ▁cave ▁to ▁be ▁sus cept ible ▁to ▁flash ▁flo oding . ▁▁ ▁In ▁October ▁ 2 0 0 9 , ▁a ▁cave ▁gate ▁was ▁installed ▁at ▁the ▁cave ▁entrance ▁to ▁preserve ▁the ▁end anger ed ▁Indiana ▁bat ▁which ▁res ided ▁in ▁the ▁cave , ▁as ▁a ▁joint ▁effort ▁between ▁Saint