▁was ▁likely . ▁ ▁Description ▁The ▁ru ins ▁of ▁Se chin ▁B ajo ▁cover ▁an ▁area ▁of ▁about ▁. ▁The ▁cer emon ial ▁center ▁of ▁the ▁ru in ▁consists ▁of ▁three ▁monument al ▁constru ctions ▁d ating ▁from ▁different ▁times . ▁The ▁" First ▁Ed ifice " ▁or ▁" First ▁Building " ▁is ▁the ▁oldest , ▁initially ▁consisting ▁of ▁a ▁platform ▁ ▁square ▁built ▁of ▁rocks ▁and ▁ad obe ▁brick ▁and ▁raised ▁ 2 ▁meters ▁over ▁sun ken ▁circular ▁pla zas . ▁The ▁sun ken ▁circular ▁pla za ▁feature ▁was ▁maintained ▁throughout . ▁In ▁one ▁iteration , ▁cal ibr ated ▁radi oc ar bon ▁d ating ▁of ▁the ▁First ▁Building ▁ranges ▁from ▁as ▁early ▁as ▁ 3 7 0 0 ▁BC ▁and ▁as ▁late ▁as ▁ 2 9 0 0 ▁BC ▁during ▁the ▁pre - cer am ic ▁( p rior ▁to ▁the ▁use ▁of ▁pot tery ) ▁period ▁of ▁Per uv ian ▁arch ae ology . ▁The ▁First ▁Building ▁was ▁re construct ed ▁on ▁five ▁occasions ▁during ▁that ▁time ▁period ▁with ▁pla zas ▁and ▁st air cases ▁being ▁constructed , ▁filled ▁in , ▁and ▁re construct ed ▁on ▁multiple ▁occasions . ▁ ▁The ▁oldest ▁of ▁the ▁sun ken ▁pla zas ▁was ▁radio ▁carbon ▁dated ▁at ▁ 3 5 0 0 ▁BC ▁in ▁ 2 0 0 8 . ▁An ▁ad obe ▁fr ie ze ▁was ▁dated ▁at ▁ 3 6 0 0 ▁BC . ▁The ▁fr ie ze , ▁ ▁tall , ▁is ▁of ▁a ▁man ▁holding ▁something ▁in ▁one ▁hand ▁and