, ▁while ▁in ▁the ▁third ▁the ▁blocks ▁are ▁very ▁well ▁joint ed , ▁and ▁the ▁faces ▁smooth ed ; ▁they ▁are ▁mostly ▁pol yg onal ▁in ▁form ▁and ▁are ▁much ▁larger ▁( the ▁maximum ▁about ▁ 3 ▁by ▁ 2 ▁m ) ▁than ▁those ▁of ▁the ▁city ▁wall . ▁A ▁flat ▁surface ▁was ▁formed ▁partly ▁by ▁sm o othing ▁off ▁the ▁rock ▁and ▁partly ▁by ▁the ▁ere ction ▁of ▁huge ▁terra ce ▁walls ▁which ▁rise ▁to ▁a ▁height ▁of ▁over ▁, ▁en clos ing ▁a ▁roughly ▁rect angular ▁area ▁of ▁. ▁Two ▁approaches ▁to ▁the ▁cit adel ▁were ▁constructed , ▁both ▁passing ▁through ▁the ▁wall ; ▁the ▁open ings ▁of ▁both ▁are ▁rect angular . ▁The ▁arch it ra ve ▁of ▁the ▁larger , ▁known ▁as ▁Port a ▁Mag giore , ▁measures ▁about ▁ ▁in ▁length , ▁ ▁in ▁height , ▁ ▁in ▁thick ness ; ▁while ▁that ▁of ▁the ▁smaller ▁is ▁decor ated ▁with ▁three ▁ph al li ▁in ▁relief . ▁Later , ▁though ▁probably ▁in ▁ancient ▁times , ▁a ▁r amp ▁was ▁added ▁on ▁the ▁northern ▁side . ▁In ▁the ▁centre ▁of ▁the ▁ar x ▁was ▁a ▁building ▁on ▁the ▁site ▁of ▁the ▁present ▁c athedral , ▁of ▁which ▁only ▁a ▁small ▁portion ▁is ▁preserved . ▁Rem ains ▁of ▁a ▁high - press ure ▁aqu ed uct , ▁which ▁supplied ▁the ▁town ▁with ▁water ▁and ▁was ▁constructed ▁with ▁other ▁public ▁buildings ▁by ▁L . ▁Bet il ien us ▁Var us , ▁may ▁still ▁be ▁trac ed . ▁A ▁temple ▁was ▁exc