▁bas in ▁is ▁a ▁struct ural ▁de pression ▁running ▁from ▁n ortheast ▁to ▁south west ▁in ▁the ▁O re ▁Mountain ▁pen ep lain ▁that ▁is ▁filled ▁with ▁Dev onian ▁and ▁Car bon ifer ous ▁sed iments . ▁The ▁main ▁communic ations ▁from ▁the ▁O re ▁Mountains ▁follow ▁the ▁valle ys ▁down hill ▁and ▁are ▁collected ▁by ▁a ▁major ▁route way ▁to ▁the ▁north ▁that ▁follows ▁this ▁fur row ▁and ▁passes ▁through ▁the ▁cities ▁of ▁Z wick au ▁and ▁Chem nitz . ▁ ▁According ▁to ▁current ▁categor isation ▁the ▁Upper ▁Ple iß eland ▁( Ob ere ▁Ple iß eland ), ▁immediately ▁to ▁the ▁east ▁of ▁the ▁towns ▁of ▁W erd au ▁and ▁C rim mit schau , ▁is ▁also ▁counted ▁as ▁part ▁of ▁the ▁bas in . ▁ ▁The ▁O re ▁Mountain ▁Bas in ▁is ▁an ▁important ▁centre ▁of ▁population ▁in ▁Sax ony ▁and ▁a ▁histor ically ▁important ▁industrial ▁region , ▁not ▁least ▁because ▁of ▁the ▁Z wick au ▁Field ▁which ▁contained ▁most ▁of ▁East ▁Germany ' s ▁very ▁minor ▁res erves ▁of ▁coal ▁and ▁included ▁the ▁biggest ▁former ▁hard ▁coal ▁min ing ▁region ▁in ▁Sax ony . ▁ ▁References ▁▁ ▁Category : Ge ography ▁of ▁the ▁O re ▁Mountains ▁Category : N atural ▁regions ▁of ▁Sax ony ▁Category : Bas ins ▁of ▁Germany <0x0A> </s> ▁Fire bug ▁is ▁a ▁dis cont in ued ▁free ▁and ▁open - source ▁web ▁browser ▁extension ▁for ▁Moz illa ▁Firefox ▁that ▁facil itated ▁the ▁live ▁debugging , ▁editing , ▁and ▁monitoring ▁of ▁any ▁website ' s ▁CSS ,