▁blocks ▁were ▁in ▁a ▁large ▁rect angular ▁building . ▁The ▁rect angular ▁building ▁was ▁focused ▁on ▁ind oor ▁group ▁labor ▁with ▁a ▁staff ▁contin ually ▁pat rolling . ▁ ▁The ▁A ub urn ▁system ▁was ▁a ▁marked ▁difference ▁from ▁the ▁earlier ▁Pennsylvania ▁plan ▁popular ized ▁at ▁Eastern ▁State ▁Pen it enti ary ▁in ▁which ▁cell ▁blocks ▁radi ated ▁out ▁from ▁a ▁central ▁building ▁and ▁was ▁the ▁original ▁design ▁for ▁the ▁nearby ▁Dis cipl inary ▁Bar ra cks ▁before ▁it ▁was ▁torn ▁down ▁and ▁replaced ▁by ▁a ▁totally ▁new ▁prison . ▁ ▁The ▁St . ▁Louis , ▁Missouri ▁architecture ▁firm ▁of ▁E ames ▁and ▁Young ▁designed ▁both ▁Le aven worth ▁and ▁the ▁United ▁States ▁Pen it enti ary , ▁Atlanta . ▁Le aven worth ' s ▁prison ▁cells ▁are ▁back ▁to ▁back ▁in ▁the ▁middle ▁of ▁the ▁structure ▁facing ▁the ▁walls . ▁The ▁prison ' s ▁walls ▁are ▁ ▁high , ▁ ▁below ▁the ▁surface ▁and ▁ ▁long ▁and ▁enc lose ▁. ▁Its ▁dom ed ▁main ▁building ▁was ▁nick named ▁the ▁" Big ▁Top " ▁or ▁" Big ▁House ." ▁The ▁dom ed ▁Dis cipl inary ▁Bar ra cks ▁two ▁miles ▁( 3   km ) ▁to ▁the ▁north ▁was ▁nick named ▁the ▁" L ittle ▁Top " ▁until ▁it ▁was ▁torn ▁down ▁in ▁ 2 0 0 4 ▁and ▁replaced ▁with ▁a ▁newer ▁structure . ▁ ▁Historical ▁tim eline ▁▁ 1 8 2 7 : ▁Colonel ▁Henry ▁Le aven worth ▁chose ▁site ▁for ▁new ▁fort . ▁▁ 1 8 7 5 : ▁Fort