▁long ships ▁or ▁traditional ▁kn ar rs , ▁but ▁as ▁German ▁mer ch ants ▁introduced ▁the ▁sea - going ▁deep - dra ug ht ▁c ogs , ▁the ▁stra its ▁and ▁streams ▁at ▁the ▁mouth ▁of ▁Lake ▁M ä lar en ▁became ▁ins ur mount able ▁obst acles ▁which ▁thus ▁created ▁a ▁need ▁for ▁a ▁trad ing ▁post ▁at ▁the ▁location . ▁ ▁While ▁the ▁oldest ▁traces ▁of ▁human ▁activities ▁in ▁present ▁Stockholm ▁are ▁consider ably ▁older , ▁the ▁development ▁as ▁described ▁above ▁preced ed ▁the ▁foundation ▁of ▁the ▁city ▁on ▁its ▁present ▁location . ▁ ▁However , ▁Bir ka , ▁S igt una , ▁and ▁Stockholm ▁forms ▁a ▁series ▁of ▁urban ▁structures ▁which ▁can ▁be ▁thought ▁of ▁as ▁the ▁capital ▁of ▁the ▁Lake ▁M ä lar en ▁region , ▁at ▁a ▁few ▁occasions ▁re located ▁to ▁fit ▁into ▁the ▁so cio - e conom ic ▁structure ▁of ▁the ▁day . ▁ ▁I cel and ic ▁sag as ▁▁ ▁The ▁water course ▁passing ▁south ▁of ▁the ▁old ▁town ▁of ▁Stockholm ▁first ▁appears ▁in ▁historical ▁records ▁as ▁the ▁somewhat ▁crypt ic ▁phrase : ▁" What ▁split ▁off ▁is ▁called ▁Stockholm " ▁( Sto ck holm ▁heter ▁det ▁som ▁sp rack ▁av ), ▁found ▁in ▁a ▁version ▁of ▁the ▁S aga ▁of ▁the ▁Saint ▁O la f ▁by ▁the ▁I cel and ic ▁author ▁St ym er ▁Fro de , ▁preserved ▁through ▁a ▁manuscript ▁from ▁the ▁ 1 4 th ▁century . ▁ ▁St ym er ▁explains , ▁what ▁today ▁are ▁the ▁islands ▁ ▁S