▁, ▁in ▁the ▁territory ▁of ▁the ▁city ▁of ▁Dort mund ▁and ▁the ▁districts ▁of ▁En ne pe - R u hr - K re is ▁and ▁Un na ▁in ▁the ▁German ▁state ▁of ▁North ▁Rh ine - West phal ia . ▁The ▁hills ▁form ▁part ▁of ▁the ▁eastern ▁R hen ish ▁Mass if ▁and , ▁to ▁a ▁less er ▁extent , ▁to ▁the ▁Berg - Mark ▁Hills ▁( B erg isch - M är k isches ▁H üg ell and ). ▁ ▁Geography ▁ ▁Location ▁ ▁The ▁Ar de y ▁Hills , ▁together ▁with ▁the ▁H aar str ang , ▁run ▁from ▁east ▁to ▁west , ▁separ ating ▁two ▁major ▁natural ▁units : ▁the ▁West phal ian ▁Low land ▁including ▁the ▁Em scher ▁De pression ▁and ▁Hell weg b ör de ▁in ▁the ▁north ▁from ▁the ▁Sü der ▁U pl ands ▁and ▁lower ▁S auer land ▁in ▁the ▁south , ▁the ▁Ar de y ▁being ▁counted ▁as ▁part ▁of ▁the ▁Sü der ▁U pl ands ▁and ▁the ▁H aar str ang ▁the ▁West phal ian ▁Low land . ▁ ▁From ▁a ▁top ographical ▁perspective , ▁the ▁Ar de y ▁Hills ▁are ▁the ▁western ▁fo oth ills ▁of ▁the ▁sp ars ely ▁wood ed ▁and ▁mainly ▁agricult ural ▁H aar str ang . ▁However ▁it ▁is ▁different , ▁not ▁only ▁from ▁a ▁cultural ▁landscape ▁point ▁of ▁view , ▁but ▁also ▁ge olog ically ▁( a ▁decis ive ▁factor ▁being ▁the ▁carbon ifer ous ▁boundary ▁near ▁the ▁surface ). ▁ ▁In ▁the ▁north , ▁on