https://mysteria.co/sites/bulverket-lake-fortress-gotland
Bulverket Lake Fortress (Tingstäde Träsk, Gotland) — Earthwork in Sweden · Mysteria
Massive 1130s timber platform fortress in Tingstäde Träsk lake, Gotland: 170 × 170 m square bulwark of ca. 25,000 pine logs forming a square grid with causeway...
lake fortressin swedenbulverketgotlandearthwork