>>2037857
Roman camps are based so that's a fine choice.
It might not even be that far-fetched for vikangz to construct similar camps themselves. If I recall correctly, there are archaeological finds in scandinavia containing roman coins and loot from military campaigns, which might suggest that men traveled south to serve as auxiliaries in roman legions as early as the 4th century. If true, they likely would have learned how to construct roman forts and brought that knowledge home with them after their service.