Harald Bluetooth built some amazing fortifications for his period of time: https://en.m.wikipedia.org/wiki/Viking_ring_fortress https://en.m.wikipedia.org/wiki

Harald Bluetooth built some amazing fortifications for his period of time: https://en.m.wikipedia.org/wiki/Viking_ring_fortress https://en.m.wikipedia.org/wiki/Viking_ring_fortress https://www.researchgate.net/publication/263286349_A_Palisade_Fit_for_a_King_Ideal_Architecture_in_King_Harald_Bluetooth's_Jelling https://www.researchgate.net/publication/263286349_A_Palisad...