, ▁and ▁these ▁logs ▁pres umably ▁gave ▁the ▁entire ▁city ▁its ▁present ▁name , ▁Stock - holm , ▁" Log - Is let ". ▁ ▁Any how , ▁any ▁hypothesis ▁on ▁the ▁origin ▁of ▁the ▁city ▁necessarily ▁need ▁to ▁depart ▁from ▁three ▁poor ly ▁documented ▁def ensive ▁structures : ▁ ▁Some ▁kind ▁of ▁original ▁primitive ▁red ou bt ▁surrounded ▁by ▁wooden ▁bar riers ▁probably ▁constructed ▁during ▁the ▁Vik ing ▁era ▁( i . e . ▁around ▁ 1 0 0 0 ). ▁ ▁A ▁ba iley ▁and ▁a ▁larger ▁building ▁located ▁on ▁a ▁pair ▁of ▁is lets ▁now ▁part ▁of ▁Hel ge and sh ol men ▁accompanied ▁by ▁a ▁row ▁of ▁pol es ▁forming ▁a ▁bar rier ▁in ▁the ▁stra it ▁( i . e . ▁the ▁" lock " ▁of ▁Lake ▁M ä lar en ). ▁ ▁A ▁castle ▁built ▁on ▁the ▁north - e astern ▁corner ▁of ▁Stad sh ol men , ▁a ▁construction ▁probably ▁initi ated ▁by ▁Bir ger ▁Jar l ▁in ▁the ▁mid ▁ 1 3 th ▁century ▁and ▁completed ▁around ▁ 1 3 0 0 . ▁ ▁It ▁is ▁possible ▁the ▁construction ▁of ▁this ▁castle ▁started ▁simultaneously ▁with ▁the ▁second ▁def ensive ▁structure ▁mentioned ▁above ▁and ▁that ▁this ▁structure ▁became ▁out dated ▁as ▁the ▁castle ▁was ▁completed . ▁It ▁is ▁often ▁said ▁the ▁keep ▁of ▁the ▁Three ▁Crown ▁Castle ▁origin ated ▁from ▁at ▁least ▁parts ▁of ▁these ▁def ensive ▁structures . ▁ ▁As ▁historical ▁and ▁arch ae ological ▁records ▁are ▁fragment ary , ▁the ▁origin ▁of ▁this ▁tower