amp art ▁around ▁the ▁Out er ▁Town . ▁There ▁was ▁clearly ▁a ▁fair ▁amount ▁of ▁open ▁ground ▁inside ▁the ▁ear then ▁r amp art . ▁Hen ning ▁con cludes ▁that ▁the ▁settlement ▁was ▁initially ▁built ▁for ▁military ▁and ▁strateg ic ▁reasons , ▁and ▁could ▁not ▁really ▁be ▁considered ▁a ▁typical ▁city ▁( with ▁all ▁of ▁the ▁associated ▁trade , ▁production , ▁and ▁population ) ▁until ▁the ▁period ▁after ▁Bulg aria ▁converted ▁to ▁Christian ity ▁in ▁ 8 6 4 / 5 . ▁Most ▁of ▁the ▁stone ▁architecture ▁in ▁Pl iska ▁was ▁built ▁between ▁this ▁conversion ▁and ▁event ual ▁By z antine ▁con quest ▁of ▁the ▁city ▁in ▁ 9 7 1 . ▁ ▁The ▁buildings ▁from ▁this ▁era ▁show ▁a ▁clear ▁By z antine ▁influence ▁in ▁their ▁design ▁and ▁function . ▁For ▁example , ▁a ▁ 4 ▁kilomet re - long ▁canal ▁fed ▁a ▁large ▁brick ▁c is tern ▁that ▁moved ▁water ▁from ▁the ▁K riv a ▁river ▁to ▁the ▁Inner ▁Town ▁via ▁cer am ic ▁pip es . ▁ ▁This ▁c is tern ▁had ▁attached ▁rooms ▁containing ▁private ▁bath s . ▁ ▁Only ▁certain ▁parts ▁of ▁the ▁arch ae ological ▁site ▁of ▁the ▁city ▁have ▁been ▁properly ▁investig ated . ▁One ▁of ▁the ▁most ▁thoroughly ▁research ed ▁is ▁the ▁As ar - d ere ▁area ▁just ▁to ▁the ▁west ▁of ▁the ▁stone ▁fort ification ▁surrounding ▁the ▁Inner ▁Town . ▁Four ▁cl ay - made ▁furn aces ▁have ▁been ▁discovered ▁in ▁this ▁area , ▁suggesting ▁that ▁Pl iska ▁possessed ▁a ▁special ized ▁pot