, ▁which ▁are ▁up ▁to ▁, ▁are ▁located ▁in ▁the ▁eastern ▁part ▁of ▁the ▁M ü ritz ▁National ▁Park . ▁The ▁hills ▁were ▁first ▁mentioned ▁in ▁an ▁official ▁document ▁dated ▁ 1 5 6 9 . ▁This ▁states ▁that ▁der ▁Schwe ing ah rd ische ▁See ▁zwischen ▁Z er ra hn schen ▁und t ▁Gold bow ischen ▁Hol tz ▁be legen ▁(" the ▁Schwe ing arten ▁lake ▁is ▁located ▁between ▁the ▁Ser ra hn ▁and ▁the ▁Gold bow ▁Wood s "). ▁ ▁During ▁the ▁period ▁ 1 6 1 4 ▁to ▁ 1 6 2 3 , ▁documents ▁record ▁the ▁sale ▁of ▁building ▁tim ber ▁and ▁fire wood ▁from ▁the ▁Z er ra hn schen ▁Ber gen . ▁ ▁After ▁that , ▁the ▁forest ▁must ▁have ▁been ▁th inned ▁so ▁much ▁before ▁the ▁mid - 1 6 th ▁century ▁that ▁by ▁the ▁end ▁of ▁that ▁century ▁large ▁f lock s ▁of ▁sheep ▁gra zed ▁the ▁Ser ra hn ▁Hills ▁from ▁time ▁to ▁time . ▁▁▁ ▁At ▁the ▁end ▁of ▁the ▁Th irty ▁Years ' ▁War ▁much ▁of ▁the ▁surrounding ▁area ▁was ▁dev ast ated ▁and ▁the ▁forest ▁spread ▁again . ▁Thus ▁in ▁ 1 6 8 8 ▁we ▁hear ▁that ▁the ▁Z er ra hn schen ▁Ber ge ▁st et ▁re ich ▁von ▁E y chen ▁M ast ▁und t ▁dann en ▁Hol tz , ▁und t ▁können ▁dar in ▁fe ist ▁gem acht ▁werden ▁ 4 6 5 ▁Schwe ine ▁( the ▁" Ser ra hn ▁Hills ▁are ▁rich ▁in ▁o ak