Gross Hausen - Girmau-2 - Aestii (aka Pruzzi) castle of the 1st Millenium

Similar castles were also erected in Britain, eg the Maiden Castle, backdated to the 6th Century B.C. Also in Ireland - thousands of similar ringforts: vool.ie/everyr...
Of interest is the note by Tacitus (1st Century A.D.) that the language of Aestii at the Sambia peninsula on the Eastern coasts of the Baltics was also similar to the language spoken in Britain).

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For convenience, the exact location is 54.860631, 19.994165